XXX V] TRIGONOCARPUS 319 



outer flesh (sarcotesta), a sclerotesta, and probably in most cases 

 an endotesta or inner flesh. The ribs of the sclerotesta are in 

 the majority of genera in multiples of three and in position corre- 

 spond to the outer ring of vascular bundles. The presence of 

 lacunar tissue in the sarcotesta of several genera may be correlated 

 with dispersal by water. The apical region of the integument 

 is not lobed but extends as a longer or shorter micropylar tube 

 above the summit of the nucellus. In the differentiation of the 

 testa, the form of the pollen-chamber, and in some other features, 

 the seeds of this group present a general agreement with those of 

 recent Cycads. 



The microspores are multicellular and larger than those of 

 the Lagenostomales : in Stephanospermum akenioides they measure 

 160/4 x 100/4 1 while in Aetheotesta 2 they reach 360/4 x 290/4. 



Genera. Trigonocarpus ; Tripterospermum ; Ptychotesta ; 

 Hexapterospermum ; Polypterospermum ; Pachytesta ; Stephano- 

 spermum ; Polylophospermum ; Codonospermum ; Aetheotesta ; 

 Eriotesta ; Gaudrya. 



Trigonocarpus. Brongniart. 



A description of the morphological features of Trigonocarpus 

 Parkinsoni and T. shorensis is given in the chapter on Medullosa 

 (p. 117), as there is good evidence that they are the seeds of that 

 genus. There is considerable difference in size and to some extent 

 in the form of casts included in Trigonocarpus and, in the absence 

 of anatomical data, it is hardly possible to determine the actual 

 systematic position of many of the specimens so named. Dr Arber 3 

 has recently proposed a new generic name Schizospermum for 

 casts very like those of T. Parkinsoni, but distinguished by the 

 splitting of the shell into three valves, a character which leads 

 him to conclude that it is the external surface which is preserved 

 and not a mere cast of the seed-cavity. It is, however, more 

 probable that the specimens are casts of a split sclerotesta. In 

 Trigonocarpus pusillus* the shell is divided into three valves, 

 the dividing lines being marked by greatly reduced ribs, and 

 in T. schizocarpoides Grand'Eury 5 , a species that may not be a 



1 Oliver (04) B. p. 376. 2 Renault (96) A. p. 272. 



3 Arber, E. A. N. (14) p. 103, PI. vm. figs. 4850. 



4 Brongniart (81) PI. B. fig. 3. 5 Grand'Eury (77) A. PI. xv. fig. 1. 



