Transactions and Proceedings of the New Zealand Institute [electronic resource]

Volume 60, 1930

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Classification.

For the purpose of identification in the field and in the herbarium, it is not usually necessary to follow the development of the carpogonial organs, and as to do this would present many difficulties, the easier course of defining the species from the fully mature plant has been adopted here. The following description of the genus therefore will probably be sufficient for our purposes.

Genus Gigartina.—Thallus cylindrical, flattened or foliose, usually thick and fleshy, corneous when dry, more or less profusely pinnately, dichotomously or irregularly branched. Usually beset with fertile ramuli of limited growth, bearing the cystocarps, simple or branched, growing from the margin of the branch or from the surface of the lamina. Cystocarps on the fertile ramuli, singly or in more or less dense clusters, usually spherical or approximately so, and partially embedded in the tissue of the ramulus, sometimes surrounded by an adnate involucre of ramuli, or surmounted by one or more linear processes. Nucleus compound and surrounded by a net work of filaments. Structure of two tissues, the inner of anastomosing threads loosely woven into a net, and passing into the outer cortical layer of moniliform vertical filaments, imbedded in firm gelatine. Tetraspores numerous in subprominent sori, below the superficial stratum, cruciately divided.

Agardh (1899), pp. 1–42, lists and classifies sixty-nine species, and in this paper we shall follow to a large extent his classification, though it is not altogether satisfactory. The genus is exceptionally well-developed in New Zealand, which contains more than a third of the species listed, and many of these are endemic. It is possible, as has been suggested, that the genus should be split up into several genera, but though many of the species are highly polymorphic, yet all exemplify the general characters as given above. In this paper we exclude all forms with broadly expanded laminae.

The following classification is based on that of Agardh, but considerably modified.

Division A.—Frond partly or altogether cylindrical.

Tribe 1.—Cylindratae. Frond cylindrical throughout or in part slightly compressed, pinnately decompound.

1. G. divaricata Hook. f. et Harv.

Tribe 2.—Aciculares. Thallus sub-terete, more or less decompound, quadrifariously branched, terminal branches subulate, fertile ramuli unaltered, cystocarps lateral on the pinnae or the genuflexed fertile ramulus.

2. G. Chapmanni Hook. f. et Harv.

3. G. Kroneana Rabenh.

Tribe 3.—Pistillatae. Sterile frond somewhat rounded below at least, more or less evidently dichotomous and decompound with the

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branches produced to a point, margins of fertile branches beset with the cystocarpic pinnules, generally opposite, with the cystocarps few or many globose, or clavate sometimes subsecund along the upper margin of the pinnule, becoming apparently terminal by the abortion of the apex of the ramulus.

4. G. macrocarpa J. Ag.

5. G. clavifera J. Ag.

(G. disticha Sond. species excludenda).

6. G. flabellata J. Ag.

Division B.—Thallus compressed or flat, branching normally dichotomous, but sometimes decompoundly pinnate, the position of the cystocarps varying according to the mode of development of the frond.

Tribe 1.—Palmatifidae. Frond flattened almost from the base, and with decompound segments going out from the margin, the primary sub-dichotomous, the lowest more elongated, the uppermost reduced, with the lobes of the latter cuneate rotund, diverging, sub-palmately; the cystocarps occupying the unaltered terminal ramuli, sub-singly behind the apex of the lobe.

7. G. laciniata J. Ag.

Tribe 2.—Pinnatilobae, with the frond above the lowest part compressed, flattened, pinnately decompound, lobes sometimes developed to a point but more often obtuse, cystocarps occupying the terminal unaltered ramuli, sub-singly behind the apex of a lobe.

8. G. livida (Turn.) J. Ag.

Tribe 3.—Prolificantes. Frond above the lowest part compressed flattened and the branches generally drawn out into a point, the whole usually more or less dichotomously decompound (though pinnated at times), the fertile ramuli emerging from the edge of the frond or from the surface of the lamina. Cystocarps sub-single to numerous behind the apex of the ramulus, which is simple or branched.

9. G. protea J. Ag.

10. G. marginifera J. Ag.

11. G. polyglotta J. Ag.

(G. volans C. Ag. A foliose form, not further dealt with here).

12. G. decipiens Hook. f. et Harv.

Tribe 4.—Innocuae. Frond pinnately decompound and distichous, pinnae sometimes narrow and linear, sometimes more dilated, lanceolate flattened, cystocarps papillose in the disc of the pinnae, sometimes singly at the apex of the pinnae which overtops it or by disappearance of the tip, terminal, or many in an elongated, branched, often crooked ramulus.

13. G. Chauvinii (Bory) J. Ag.

Division C.—Without special fertile ramuli, and with the frond on one side more or less channelled or concave on the other angular or convex, sometimes teretely stipitate below, the upper part more or less expanded, the position of the cystocarps varying with the mode of branching.

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Tribe l.—Alveatae.The frond channelled with all parts more or less similar, the lower and uppermost almost equally narrow linear, the apices sometimes obtuse, sometimes produced into a point.

14. G. alveata J. Ag.

15. G. ancistroclada Mont.

16. G. angulata J. Ag.

(G. Burmanni (C. Ag.) J. Ag. Species excludenda).

17. G. insidiosa J. Ag.

Tribe 2.—Stipitatae. Frond above the somewhat terete base, somewhat expanded into cuneate segments, bearing the cystocarps on the concave side.

18. G. tuberculosa Rabenh.

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