CORDAITALES 



177 



above, under Cordaianthus Williamsonii, that there can be no reason- 

 able doubt that the seeds belong to Cordaitales. Cycadinocarpus of 

 Renault is interesting from the fact that the inner set of vascular 

 strands does not enter the nucellus, but is said to traverse the inner 

 layer of the testa, which in this case must be the third or " inner fleshy " 

 layer. This distribution of the 

 vascular strands is the same 

 as in the seeds of Cycadales. 



The seeds known as iJ/saMo- 

 carpus, formerly supposed to 

 be forms of Cordaicarpus 

 (Cdrdiocarpus) and therefore 

 belonging to Cordaites, have 

 been found by Grand 'Eury 

 (16) associated with leaves 

 believed to be those of Poro- 

 xylon. If this connection is 

 confirmed, the inclusion of 

 Poroxylon among the Cor- 

 daitales would seem to have 

 passed the doubtful, stage. 



Since the investigation of 

 the testa of the seeds of cycads 

 by Miss Stopes (15), in which 

 it was made clear that the testa 

 is differentiated into three 

 layers (outer fleshy, stony, and 

 inner fleshy), the temptation 



is to read this structure into the interpretations of the seeds of Cordai- 

 tales and Cycadofilicales, and there seems to be enough confirmation 

 of such an interpretation to justify it in some cases. It is conceivable 

 that the inner fleshy layer, which in cycads contains the inner set of 

 vascular strands, might be confused with the peripheral region of the 

 nucellus, provided the testa and nucellus are organically continuous, 

 as in modern seeds. In such cases the inner fleshy layer would be 

 distinct only in the free part of the integument, and since in the testa 

 stage it becomes merely a papery layer, it might not be recognizable 



Fig. 209. — Cordaianthus Grand 'Euryi: 

 section o£ beak of nucellus; wedged in 

 the passageway are two large pollen grains, 

 the lower one showing part of the surface 

 of the exine and also the multicellular interior; 

 X225. — After Renaxh-t (3). 



