Art. XXVI—The Norfolk Island Species of Pteris.*
[Read before the Philosophical Institute of Canterbury, 7th July, 1915.]
Since drawing up the list of ferns for my paper on the flora of Norfolk Island (Trans. N.Z. Inst., vol. 47, p. 1) I have received a large number of additional specimens from my father, Mr. W. Laing, resident on the island. These necessitate a reconsideration of the species of the genus Pteris. This revision need not include the common Pteridium esculentum (Forst. f.) Cockayne and P. comans, as to whose occurrence on the island all are agreed. The following table shows roughly how Endlicher's species have been viewed in recent literature:—
|? P. tremula||= P. Baueriana||= Doubtful species.|
|? P. incisa||= P. Brunoniana||= P. incisa.|
|? P. quadriaurita||= P. Zahlbruckneriana||= P. comans.|
|P. tremula var. Kingiana||= P. Kingiana||= P. tremula.|
|? P. quadriaurita||= P. Trattinickiana||= Doubtful species.|
Now, it is probably impossible without direct reference to the type specimens at Vienna to determine with certainty the identity of Endlicher's plants; but I think that it can be done more accurately than has yet been done, if fairly full material is available.
The first important point to consider is the question of the venation, whether forking or anastomosing; and an examination of Endlicher's descriptions gives the following results: Veins forked—P. Baueriana, P Kingiana, P. Trattinickiana; veins anastomosing—P. Brunoniana, P comans, P. Zahlbruckneriana. It is true that no mention is made in the case of P. Baueriana as to whether the veins are free or anastomose; but as the plant is said by Endlicher to be very near P. tremula, in which the veins are free, we may consider both the same in this respect.
A. Species with Forked Venation.
(a.) Pteris tremula R. Br. = Pteris Baueriana Dies., Endl., No. 37.
Let us consider the forms with forked venation first. I have three of these which agree well with Endlicher's descriptions of P. Baueriana, P. Kingiana, and P. Trattinickiana. I have little doubt that they are distinct species. Endlicher's diagnosis scarcely serves to separate P Baueriana from P. Kingiana, but his detailed description enables this to be done with a fair amount of accuracy, and there seems to be but little doubt that P. Baueriana Dies. = P. tremula R. Br. In this I follow Maiden, though Endlicher himself admits that P. Baueriana is “Pteridi tremulae R. Br. proxime affinis.” Hooker and Baker do not mention this species.
A comparison of specimens from Norfolk Island of this plant with the New Zealand Pteris tremula shows that the two forms are almost indistinguishable.
[Footnote] * Specimens of these and other Norfolk Island plants collected by me will be found m the Canterbury Museum.
(b.) Pteris Kingiana Endl., No. 40.
“Pteris Kingiana, frondis coriacea 3-partitae ramis pinnatis pinnis pinnatifidis glaberrimis, laciniis lineari-subfalcatis acutrusculis integerimis.”
There is not very much in this diagnosis to separate the plant from P. Baueriana. P. Baueriana is said to be bipinnate; but both forms
I have are bipinnate only at the base, and tripartite generally; and the distinction in this case seems to me to be one that is unimportant, depending a good deal upon the luxuriance of growth However, the two species, if I understand them rightly, are easily separated by the shape of the frond and of the pinnules, and by the consistency of the frond, colour
of the stipes, &c. They are quite distinct in appearance, and not likely to be confused. These points are mostly noted in the detailed description of Endlicher, and I have little hesitation in stating that the species P. Kingiana will have to be revived. The following is the fuller description of the species as given by Endlicher: “Filix subbipedalis, stipite pennae columbinae crassitie rubro-fusco, glaberrimo, nitido, antice profunde sulcato. Frons coriacea glaberrima, 3-partita. Rami pinnati; pinnis' pinnatifidis; laterales in specimine observato 9-pollices longi, erecto-patentes, utrinque pinnis 3–4 onusti; pinnae approximatim alternae, sub-sexpollicares, inferior supremi et infimi paris dimidio fere brevior v. plane nana. Rami medii pinnae alternatim collaterales, utrinque 5–6 erecto-patentes, omnes usque ad costam pinnatifidae. Laciniae coriaceae lineari-subfalcatae acutiusculae integerrimae glaberrimae suboppositae, rami medii pollicares, 2 ½ lineam latae, lateralium 7-lineas longae, latitudine 3-lineari, obtusiusculae, omnes basi deorsum dilatatae sinu acuto disjunctae; terminalis elongata. Nervus laciniarum prominulus, venulas alternas, prope basim late 2-furcas exserens. Indusia membranacea, ½ lineam lata, paullo supra basim laciniae axorta, infra apicem desinentia.”
This is readily distinguished from P. tremula by its much smaller size, much more broadly deltoid frond, much more coriaceous texture, smaller number of (3–4) pinnae on each side. The pinnules also are quite distinct from those of P. tremula, being much more falcate in outline, less rounded at the tips, and increasing in breadth towards the base. Hooker and Baker (Syn. Fil, p. 161) refer to P. Kingiana as a variety (B) of P. tremula “with the ultimate segments larger, sometimes 1 ½ in. long, nearly ¼ in. broad, without being toothed “; and state it “was originally published from Norfolk Island, but some New Zealand specimens agree with it.”
I do not understand this except on the assumption that the form they describe is a form of P. tremula, as it might well be, and not of P. Kingiana. I have seen nothing from New Zealand at all matching P. Kingiana.
(c.) Pteris biaurita L var. quadriaurita = ? Pteris Trattinickiana Endl., No. 42.
This appears to me to be a form coming very close to the preceding. Maiden considers it as possibly the same as the widespread subtropical P. quadriaurita, which it undoubtedly closely resembles. Endlicher's diagnosis is as follows: “P. Trattinickiana, frondis membranacea 3-partitae ramis pinnatis, pinnis pinnatifidis, laciniis oblongo-linearibus obtusis discretis, argute serrulatis, venulis furcatis, soris interruptis.”
In P Kingiana the non-fertile portions of the frond are either entire or only slightly serrulate at the tips; in this form they are regularly serrulate throughout. In P. Kingiana the pinnae are exceptionally more than 4 on each side; in this they are usually 5 or 6. The pinnules in P. Kingiana are subfalcate; here they are oblong. The frond is also much more membranous than in P. Kingiana. It will thus be seen that it is intermediate between P Kingiana and P. tremula, but in general outline and character of frond and pinnules it approaches much more nearly to the former than to the latter.
A note is necessary regarding the indusia. They are thus described by Endlicher: “Indusia membranacea, interrupta, saepius unilateralia.” In this form and the preceding, very frequently towards the apex of the pinna the sorus is formed only on one side of the pinnule, and is much
abbreviated. I have seen no specimens, however, in which it could be said to be interrupted; and this makes the identification of my plant with P. Trattinickiana somewhat doubtful.
I have seen only one authentic specimen of P. quadriaurita, and that a South African one. A comparison shows that the form from Cape Colony has longer, narrower, and more acuminate pinnules and much more interrupted sori than the one under consideration. I am usually averse
Fig 3.—Pteris comans Forst f = ? Pteris Zahlbruckneriana Endl. A pinna of the Norfolk Island form (⅓ natural size), with a magnified fertile pinnule, a.
to identifying two species which differ somewhat and come from different areas, but think that as P. quadriaurita is the name of a well-known and widely distributed form it had better be retained here. My specimens show no fertile fronds.
B. Species with Netted Venation.
(d.) Pteris comans Forst. f. = ? Pteris Zahlbruckneriana Endl, No. 41.
Excluding Pteris comans, I have only two forms from Norfolk Island coming under this head. One of these agrees well with the description of
P. Brunoniana; and the other is P. (Histiopteris) incisa, which was apparently not collected by Bauer, but was first recorded by Müller from specimens collected by Carne Thus I have no form corresponding to P. Zahlbruckneriana Endl. Maiden considers this as perhaps the same as P. quadriaurita and P. Trattinickiana; but as these are both forked-veined this cannot be so. Christensen regards it as a synonym of P. comans, and there is certainly little in Endlicher's description to separate it from P. comans. Hooker and Baker do not record it. I have no opinion of my own to offer on the matter, and think that it may well be left as a doubtful synonym of P. comans. P. comans of the island is a much more luxuriant form than that of New Zealand, and much more membranous in texture, but scarcely otherwise different.
(e.) Pteris Brunoniana Endl., No. 38.
I quote Endlicher's description of P. Brunoniana: “Pteris Brunoniana frondibus 3-pinnatis membranaceis glaberrimis subtus glaucescentibus; foliolis alternis oppositisque, pinnulis oppositis sessilibus lanceolatis obtusiusculis, infimis basi repandis superioribus confluentibus, terminali elongato, venulis anastomosantibus. Pteridi Vespertilionis affinis. Pinnas video pedales sesquipedalesque, utrinque foliolis sessilibus subdenis duodenisve oppositis v. in altero specimine alternis, patentissimis 4–6 pollicaribus infimis sterilibus summisque brevioribus onustas. Pinnulae sessiles oppositae, patientiusculae, 10–14 lin. longae, semi pollicem latae, basi inter se coadunatae dilatatae, sub-repandae, superiores breviores confluentes, terminalis elongata angustata, 2-pollicaris, latitudine 3-lineari, basi obsolete repanda, apice integerrima acutiuscula, omnes utrinque glaberrimae, supra obscure virides, subtus glaucescentes. Venulae anastomosantes, sori continui v. rarius interrupti; indusia angustissima, demum patientiuscula. Rhachis communis partialesque glaberrimae.”
It seems to me that P. Brunoniana is quite distinct from P. incisa. with which Christensen regards it as synonymous, and Maiden doubtfully so The species P Brunoniana Endl. will therefore have to be re-established.
The following show some of the points of distinction between the Norfolk Island forms of these two species:—
|Pteris incisa.||Pteris Brunoniana.|
|1 Pinnules rounded, lanceolate to oblong or ovate||1 Pinnules deltoid.|
|2 Sori much interrupted.||2 Sori usually continuous from base of sinus to a short distance from the apex.|
|3. Sinus (in Norfolk Island forms) often nearly closed, adjacent segments sometimes overlapping.||3 Sinus open and spreading.|
|4 Indusium poorly developed.||4 Indusium well developed.|
Undoubtedly on Norfolk Island the two species are distinct, though it is possible that elsewhere there may be intermediates between P. incisa and P Brunoniana. I have left this fern under the genus Histiopteris, though further examination may show that it should be included under Pteris.
(f.) Histiopteris incisa (Thbg.) J. Sm.
A well-marked form of this fern is fairly common on Norfolk Island. It is much more luxuriant and stouter than the New Zealand plant, but otherwise scarcely different.
The results of this paper may thus be summed up in a list showing the chief forms of Pteris on the island:—
Pteridium esculentum (Forst. f.) Cockayne = Pteris esculenta Forst. f.
Pteris tremula R. Br. = P. Baueriana Dies.
Pteris Kingiana Endl. (vide Fig. 1).
Pteris biaurita L. var. quadriaurita Retz. = ? P. Trattinickiana Endl. (vide Fig. 2).
Pteris comans Forst. f. = ? P. Zahlbruckneriana Endl. (vide Fig. 3).
Pteris Brunoniana Endl. (vide Fig. 4).
Histiopteris (Pteris) incisa (Thbg.) J. Sm. (vide Fig. 5).