XXX] TEIGONOCAEPTTS 119 



showing a tMck fleshy envelope enclosing an oval kernel with 

 a hard wall prolonged upwards as a longer or shorter micro- 

 pyle. Casts of the seed-cavity are represented in figs. 423; 

 424, 2, 3. The surface of these casts occasionally shows one or 

 more short cyhndrical projections which are probably extensions 

 of the sand or mud into holes formed in the testa by boring insects. 

 The view that Trigonocarpus seeds are 'obviously Palm fruits' 

 was not accepted by Hooker and Binney who inchned to regard 

 them as the seeds of Conifers and compared them especially with 

 the similar nuts of Ginkgo seeds (c/. fig. 631, C). It was Mr Wild^ 

 who was first struck by the association of Trigonocarpus and 

 the petioles of Medullosa (Myeloxylon) and by some resemblances 

 in structure between the testa and the hypoderm of the petioles ; 

 though, as Scott and Maslen^ point out, the agreement is not so 

 close as Wild believed, his view of a possible connexion between 

 the reproductive and vegetative organs has been confirmed. 

 Wilhamson extended our knowledge of the genus by his account 

 of Trigonocarpus olivaeformis Lind. and Hutt., a form that is 

 specifically identical with T. Parkinsoni Brongn. This author 

 also drew attention to the close resemblance between Brongniart's 

 three genera Trigonocarpus, Hexapterospermum, Tripterospermum 

 and expressed doubts as to the possibility of foimding specific 

 differences on casts of the Trigonocarpus type without the evidence 

 of anatomy. Our knowledge of the structure of Trigonocarpus 

 has in recent years been considerably extended by the researches 

 of OUver, Scott and Maslen, and Salisbury. 



Trigonocarpus Parkinsoni^ Brongniart. 



The seeds of this species hke all examples of the genus are 

 radiospermic, that is radially symmetrical in contrast to the 

 flattened or platyspermic seeds. The complete seed is elongate 

 oval in form when preserved as an impression (fig. 425, A) and 

 reaches a length of 4 — 5 cm. : the casts of the seed-cavity are 

 ovoid and provided with three prominent ridges (fig. 424, 2, 3). 

 The testa forms a thick covering differentiated into three regions, 

 an outer flesh or sarcotesta, a sclerous shell or sclerotesta, and 



' Wild (00). ' Scott and Maalen (07) p. 96. 



» Scott and Maslen (07). 



