69 
Trigonocarpus Shorensis , sp. nov . 
In T 7 . pusillus 1 the ribs had almost become obsolete and the sclerotesta was 
nearly circular in outline, with three commissured ribs only very slightly projecting 
(Text-fig. 8, e). 
Polylophospermum 2 possessed twelve ribs, of which six were fissured, the alter- 
nating and non-fissured ribs corresponding to the radial planes of the six sarcotestal 
bundles (Text-fig. 8, a). 
Ptychotesta and Hexapterospermum P Six-angled seeds with very prominent ribs, 
all of which in the case of the former were fissured (perhaps also in the latter) and 
enlarged at the ends, owing to the separation of the two parts in that region. 
PolypterospermumP An hexagonal seed with six acute ribs at the angles of the 
testa, and alternating with them six others which were short and blunt. 
PachytestaP A circular seed, but exhibiting, like T. pusillus , three commissures. 
The bundles had undergone considerable branching, so that not only are they 
numerous tangentially, but also form two concentric series, a complexity of vascular or- 
ganization that goes hand in hand with an elaborate internal structure (Text-fig. 8, b). 
StephanospermumP The two species were circular, and all vestiges of ribbing 
have disappeared. The sarcotesta is usually only represented by the tissue occupying 
the apical cup, so that its vascular structure is unknown. 
The species of Trigonocarpus , we see, thus form a consecutive series 
involving the gradual elimination of the secondary ribs. 
The production of ribs in relation to bundles is a phenomenon of 
widespread occurrence, met with elsewhere in the seeds of Dicotyledons, 
Gnetales, and Cycadales,as well as in the vegetative organs of many plants. 
They are probably an expression of mechanical utility, and, except from 
the taxonomic standpoint, the absence of such ribs from the seeds of 
T. Shorensis and T. corrugatus is a point of little importance. 
Disregarding the vascular ribs, the general sclerotestal structure in 
Trigonocarpus Shorensis and T . Parkinsoni is identical. Scott and Maslen 7 
remarked on the variability in development of the secondary ribs in the 
latter species, which always die out before the primary, and in some cases 
are so slightly developed as to be practically absent. The two species 
T. corrugatus and T. Shorensis constitute further stages in the reduction 
series, for in the former these ribs only extend for half the length of the 
seed, and in the latter are mere chalazal vestiges. In T. Noeggerathi only 
the primary ribs are present. And, finally, in species such as T. pusillus 
and T. elongatus all indication of the secondary ribs is lost, which applies 
almost equally to the primary ones also. It is evident that the secondary 
ridges in the genus Trigonocarpus were in an obsolescent condition, which 
would fully account for the absence of commissures jf such did, as the 
writer believes, originally exist. 
1 F. W. Oliver, New Phyt., vol. iii, 1904, pp. 96-104. 
2 F. W. Oliver, Ann. Bot., vol. xxi, 1907, pp. 303-4. 
3 Brongniart, Comptes rendus, tome lxxviii, 1874, pp. 15a, 16. 
4 Brongniart, loc. cit., p. 16. 5 F. W. Oliver, New Phyt., vol. i, No. 7, 1902. 
6 Oliver, Trans. Linn. Soc. Bot., vol. vi, 1904. ? Loc. cit., p. 107. 
