Studies of the New Zealand Nothofagus Species
2. Nut and Cupule Development
[Read before the Wellington Branch, October 20, 1949; received by the Editor, October 28, 1949]
No. 1 of this series of papers (Poole, 1950) dealt with the taxonomy and floral morphology of the New Zealand Nothofagus species as defined by Cockayne (1926). The present paper describes for these species, nut and cupule development and their morphology at maturity. As with the flowers, morphological descriptions have hitherto been incomplete or inaccurate. Formation of the seed as distinct from the nut is referred to only incidentally. The related phenomena of percentage of seed set and seed years have been described briefly (Poole, 1948), but details are left to a later paper. These phenomena are somewhat, involved, for nut development can be parthenocarpic.
Details of Development
Staminate and pistillate flowers are borne together on the one shoot, and for all species pistillate flowers were found to be receptive about the time pollen was shed from the staminate flowers on the same shoot. Where more than one pistillate flower per shoot was present the lower were receptive before the upper. The following records are an indication of the sequence of pollination that occurs in the species. While this order probably remains the same, the times vary for different districts and for different altitudes. The record for Fagus sylvatica is included as an interesting comparison.
|N. truncata||Beginning October (near Wellington. Alt. 100 m.)||Mid-September (near Wellington. Alt. 100 m.)|
|N. fusca||Mid-October (Akatarawa, near Wellington. Alt. 150 m.)||Beginning October (Akatarawa, near Wellington. Alt. 150 m.)|
|N. solandri||Mid-October (near Wellington. Alt. 100 m.)||End September (near Wellington. Alt. 100 m.)|
|N. cliffortioides||End November (near Greymouth. Alt. 200 m.)||End November (Erua. Alt. 800 m.)|
|N. menziesii||End November (Maungatua, Otago)||End November (Maungatua, Otago)|
|Fagus sylvatica||No flower||Beginning October (Wellington; ornamental trees)|
After pollination the small pistillate inflorescences develop, and in about two months the resulting cupules and nuts reach approximately
their maximum size. In from six to seven months' time the nuts are ripe and the majority are shed from the cupules.
It should be borne in mind that the inflorescence consists of a cupule split into segments which bear small bracts, the whole enveloping the pistillate flowers. The process of development then is as follows.
The cupule segments grow up from the base and the bracts form regular transverse rows on the outside of the segments. The mature cupule has a somewhat enlarged woody base from which arise three or four linear or triangular segments with transverse rows of bracts (glandular bracts in N. menziesii) on the outside. The growth of the ovaries keeps pace with that of the cupule. The incipient wings on the angles of each ovary grow into narrow wings on the developing fruit and project slightly between and above the cupule segments. At about one month after fertilisation lignification begins in the cupule tissue and in the ovary walls. Fibres are formed from meristematic tissue arising in the parenchymatous tissue of the cupule and ovary. Fibrous layers develop quickly, and well before they are ripe, both cupule and nuts are hard and woody.
The mature fruit is a woody nut, roughly oval, but with a beak. flattish or three angled with narrow wings on the angles; the wing tips project above the dead styles to form the beak.
It will be sufficient to say here that, at the time of pollination, ovules are only beginning to form and the locules develop ahead of them. About one month after pollination of the flowers it is just possible to dissect the tiny ovules from the ovaries. Two locules, each with two pendulous anatropous ovules, form in the dimerous flowers. and three locules each with two ovules in the trimerous flowers. The ovules develop to a small size and then all except one per fruit abort. This one develops until it occupies the whole of the interior of the fruit. Thus an exalbuminous nut is formed.
Parthenocarpic Development of Fruit
The cupules and nuts have the power to complete development and ripening without the setting of fertile seed. Preliminary microscopic investigations and other experiments indicate that this can be true parthenocarpic development for which no stimulus of pollination or of fertilization is necessary.
In several experiments flowering shoots had their staminate flowers removed before the pistillate flowers were receptive. The shoots were then baged to exclude any pollen. All cupules and nuts developed to maturity. but the nuts contained no fertile seed.
Parthenocarpic development appears to be normal in off seed years judging from the 1947–48 season, in the main a poor flowering year except for some areas of N. menziesii. Sparse flowering occurred from which cupules and nuts formed normally. The ovules of each nut developed until a complete embryo sac was formed, but the ovules then aborted in nearly all nuts.
Morphology of Mature Cupules
There follows a description of the mature cupules and nuts. The accompanying figures illustrate these and establish the leaf types for each species described. The material has been selected to represent
as nearly as possible average sizes. Within each species trees with cupules and nuts of slightly greater or smaller sizes are to be found. No attempt is made to describe the cupules and nuts from trees with aberrant or intermediate leaf forms belonging probably to hybrid groups.
Nothofagus fusca (Hook, f.) Oerst.
(Tree from Donnelley's Flat, Mount Holdsworth.)
(In Bot. Div. Herbarium No. 61914.) Fig. 1.
Cupule approximately spherical, about 7 mm. diam., brown and woody, consisting of four broadly lanceolate segments arising from a thickened, woody base; sometimes shortly stalked. Each segment with three well-developed, transverse, uneven bracts. Base of cupule with sparse, short hairs. Each cupule normally containing two lateral triquetrous nuts and one median flattish nut. Nuts, woody, narrow wings on the angles, sparsely hairy, straw coloured, wings sometimes undulate or coarsely toothed at the top, often twisted. Triquetrous nuts approximately 6 mm. long-by 5 mm. wide, broadly oval in outline, broader below the middle than above, the top portion with a tendency to form a break. Flat nut 6 mm. long by 5 mm. wide with the same outline as the triquetrous nuts.
Nothofagus truncata (Col.) Cockayne
(Tree from Catchpole Stream, Orongorongo.)
(Bot. Div. Herbarium No. 35057.) Fig. 2.
Cupule oval, about 8 mm. wide by 7 mm. long, brown and woody with a short thick stalk. Four broadly lanceolate segments arise from a thickened woody base. Each segment with three well-developed, transverse, uneven bracts, the topmost almost concealing the top of the segment to which it is attached. Stalk and base of cupule with dense short hairs. Each cupule normally with two lateral triquetrous nuts and one median flattish nut. Nuts woody, sparsely hairy, narrow wings on the angles, the wings towards the top of the nuts more pronounced than in N. fusca. Wings usually twisted and reddish. Triquetrous and flat nuts 7 mm. long by 5 mm. wide, urn shaped, the wings drawn out towards the top into broad beaks.
Occasionally trees are found bearing nuts approaching in shape those of N. fusca, though on fresh nuts the reddish coloration of the wings of N. truncata is sufficiently distinctive. On weathered nuts, however, the coloration disappears.
Nothofagus solandri (Hook. f.) Oerst.
(Tree from Campbell Mill Road, Akatarawa, elevation 100 m.)
(Bot. Div. Herbarium No. 64979.) Fig. 3.
Cupule claw shaped, about 5 mm. long by 4 mm. broad, brown and woody, consisting of a somewhat swollen base divided into two somewhat unevenly; sessile or shortly stalked. From the larger section two narrow lanceolate segments, and from the smaller one narrow lanceolate segment, arise. This last segment is sometimes slightly shorter than the others. Each segment with two closely fitting, transverse bracts with membranous edges. Cupule base hairy, and scattered white hairs also present on the segments. Cupule with one to three but usually with two nuts; if three, two are lateral and triquetrous
Leaves, cupules and nuts of the New Zealand species of Nothofagus. (The ab-axial surfaces of the leaves have been drawn in order to show the domatia on the leaves of N. fusca and N. menziesii.)
Fig. 1—N. fusca; leaf, lateral trimerous and central bimerous nuts, and cupule.
Fig. 2—N. truncata; as for N. fusca.
Fig. 3—N. solandri; leaf, bimerous and trimerous nuts, and cupule.
Fig. 4—N. cliffortioides; as for N. solandri.
Fig. 5—N. menziesii; leaf, lateral trimerous nuts and central aborted structure, and cupule. Fig. 6—N. menziesii with the central nut developed. Scale: leaves natural size; cupules and nuts X 1.5.
and one median and flattish; if two, one is triquetrous and one flattish; and if one, it is triquetrous. Nuts woody, narrow wings on the angles, dark straw coloured, sometimes with reddish wings, 6 mm. long by 4 mm. wide, broadly oval in outline with widest portion below the middle and a break at the top.
A variation of the number of nuts per cupule is usually to be found on individual trees and on different trees within the same population. For instance, material from D'Urville Island (collected A. Hutson) had the following number of nuts per cupule:
|Cupules with||Cupules with|
|Tree No.||one nut||two nuts|
Occasionally N. solandri trees are to be found with mainly three nuts per cupule. It is suspected however, that these trees are hybrids.
Nothofagus cliffortioides (Hook. f.) Oerst.
(Tree from Arthur's Pass, 900 m. elevation.)
(Bot. Div. Herbarium No. 65333.) Fig. 4.
Cupule claw shaped, about 5 mm. long by 3 mm. broad, shortly stalked or sessile, brown and woody, slightly viscid, consisting of a somewhat swollen base divided unevenly into two. From one half two narrow lanceolate segments and from the other half one narrow lanceolate segment or, more frequently, a short blunt segment arise. Each segment with two closely fitting transverse bracts, the topmost almost obscuring the segment tops. Each cupule has one or two nuts: if one, it is triquetrous, if two. one is triquetrous and the other is flattish. Nuts woody, narrow wings on the angles, roughly oval in outline with a beak at the top; 5 mm. long by 3·5 mm. broad; dark straw to chocolate coloured; somewhat shiny surface.
The cupules of N. solandri and N. cliffortioides are usually sufficiently distinct to be identified, but the nuts are frequently indistinguishable.
Nothofagus menziesii (Hook. f.) Oerst.
(Tree from Silverstream River. Marlhorough, 800 m. elevation.)
(Bot. Div. Herbarium No. 62143.) Figs. 5 and 6.
Cupule claw shaped, about 7 mm. long by 5 mm. wide, brown and woody with a short, squarish, densely hairy stalk; base a thickened pseudo-calyx with two lateral segments; segments of the pseudo-calyx bluntly toothed, each tooth glandular capped. From the cupule base arise four narrow segments each with its top cut into acute teeth tipped with glands; each segment has five transverse rows of projecting gland-tipped tubercles. Each cupule has three nuts, two lateral and triquetrous and one central and flat (Fig. 6), or it has two lateral nuts and a central aborted structure (Fig. 5). Nuts woody with marked wings on the angles; 6 mm. long by 4 mm. wide; on the flattish nuts one of the wings is sometimes double; tips of wings extended into gland-capped acuminate points, Nuts dark straw with paler wings.
The percentage of abortion of the central nut varies from tree to tree and sometimes on the same tree. The following figures from four trees growing at 800 m. elevation, Silverstream, a branch of the Wairau River, Marlborough (collected R. Mason) show this.
[The section below cannot be correctly rendered as it contains complex formatting. See the image of the page for a more accurate rendering.]
|Tree No.||Nuts per cupule|
|2||2 with central aborted structure|
|3 50%||2 with central aborted structure|
A summary of the characters given in the above descriptions is contained in the accompanying table. From this it will be seen that:
Based on morphology, three groupings of the nuts and cupules are apparent:
N. fusca and N. truncata have the largest cupules and nuts, four segments per cupule, and three nuts per cupule. The difference between the nuts of the two species is sometimes difficult to determine, but those of N. truncata usually have a more marked beak and wider wing at the top. This wing is also usually reddish, a character that shows up in bulk samples of fresh seed. In weathered samples this colour disappears.
N. solandri and N. cliffortioides have the smallest cupules and nuts, three segments per cupule and one to three but usually two nuts per cupule. The cupules of the two species are very similar though those of N. solandri can usually be distinguished by the hairiness of the cupule base and segments and the more regular segments. The nuts are indistinguishable. Large nuts of N. solandri sometimes look like small nuts of N. fusca or N. truncata, but the wings of the nuts of the first species are narrower.
The glandular nature and form of both cupules and nuts of N. menziesii make them quite distinct from those of the other species.
The groupings given above are the same as those shown by the floral morphology. In this grouping. N. menziesii stands out as a distinct species.
A matter of great practical importance is that for all collections of beech nuts, other than those of N. menziesii, leaf samples should be gathered at the same time, and for any accurate experimental work collections from individual trees should not be mixed.
The general development of the cupule and nut from the pistillate inflorescence is described. This may be parthenocarpic, especially in poor flowering years, and proceeds independently of seed formation. A description of mature cupules and nuts for the species as defined by Cockayne is given, and these descriptions are discussed taxonomically.
|N. fusca||N. truncata||N. solandri||N. cliffortioides||N. menz. esii|
|Stalk||Sessile or some-times short stalk||Very short stalk||Sessile or short stalk||Sessile or short stalk||Short stalk|
|Size (mm.)||± 7 x 7||± 8 x 7||± 5 x 4||± 5 x 3||± 7 x 5|
|No. of segments||4||4||3||3||4|
|(one shorter some-times than other two)||(one shorter than other two)|
|Bracts per segment||3||3||2||2||5 (carrying glands)|
|Nuts per cupule||3||3||1–3||1–2||2–3 (if 2, the third represented by an aborted structure|
|Size (mm.)||± 6 x 5||± 7 x 5||± 6 x 4||± 5 x 3.5||± 6 x 4|
|Shape||Broadly oval; broad beak; wings some-times irregular on top||Urn shape; broad beak; wings some-times twisted||Broadly oval; beak||Oval; beak||Oval with attenuate wing tips|
|Hairs||Sparse, short||Sparse, short||Sparse or glabrous||Sparse or glabrous||Sparse, short|
|Colour||Pale straw||Pale straw with reddish wings||Dark straw. Wings sometimes reddish||Dark straw to chocolate||Dark straw with paler wings|
Greatful acknowledgment is made to the many people, especially Forest Service Officers and members of the Botany Division, who have made collections upon which part of this study is based, and to C. M. Smith, Chief Inspector, Forest Service, and Miss L. B. Moore for helpful criticism.
Poole, A. L., 1948. The Flowering of Beech. N. Z. Jour. For., v.5 pp. 422-427.
— 1950. Studies of New Zealand Nothofagus Species. I. Taxonomy and Floral Morphology. Trans. Roy. Soc., vol. 78 Pp. 363-380.
Cockayne, L., 1926. Monograph of the New Zealand Beech Forests. Part 1. The Ecology of the Forests and TAxonomy of the Beeches. N. Z. State Forest Bull., No. 4. Govt. Printer, Wellington.