394 Mrs Arber, A note on Cardiocarpon compressum, Will. 



allied plants. The sclerotesta or shell consisted of two flattened 

 valves, pointed above and broadest near the base. In both length 

 and breadth these valves slightly exceeded half a centimetre. 

 In well preserved specimens the shell is enclosed in a delicate 

 sarcotesta forming a thin layer over the surface of the valves, 

 and at their lateral edges extending beyond them as a wing 

 lying in the plane of flattening. The wing appears to have 

 terminated in a short downward prolongation on each side of 

 the hilum, giving the seed a remote resemblance to a mitre. It 

 should be mentioned that Williamson took a different view of 

 the structure, and figures the sarcotesta as continuous round the 

 base of the seed. 



Williamson's preparations did not admit of his observing the 

 vascular system, which is of some interest. The main supply 

 bundle enters the hilum and expands into a funnel-shaped mass 

 below the nucellus. Here it gives off two opposite branches in 

 the plane of flattening of the seed. These branches are at first 

 horizontal, but they soon bend downwards and outwards, travers- 

 ing the shell in an oblique direction. On emerging into the 

 sarcotesta they curve upwards and run to the micropyle following 

 the slight groove at the junction of the valves. The base of the 

 nucellus is supplied by tracheides given off from the expanded 

 end of the central bundle above its two main branches. I have 

 not been able definitely to satisfy myself as to whether a nucellar 

 vascular system arises from this basal tracheal plate. 



Inside the shell there are indications of an "inner flesh," 

 which is however seldom preserved. The nucellus seems to have 

 been free from the integument from the base upwards. The 

 megaspore is usually empty and contracted, but in one case a 

 tissue occurs within it which may be a prothallus. 



I have provisionally adopted Williamson's name for this seed, 

 Cardiocarpon compressum, but it is doubtful whether it should 

 be permanently retained. The question of nomenclature, which 

 presents some difficulties in this case, will be discussed at length 

 in a detailed paper which I hope to publish shortly. 



