a 



574 STUDIES IN FOSSIL BOTANY 



though it is quite possible that here, as in most so- 

 called exalbuminous seeds, some slight remains of the 

 endosperm persisted. The small mass of tissue marked 

 e in Fig. 203, D, in which the nuclei appear to be 

 preserved, may probably be a portion of the remaining 

 endosperm, though it might also be interpreted as 

 belonging to the root-cap of the embryonic radicle. 



The embryo is very 

 well preserved, indeed 

 the Bennettiteae afford 

 the only cases in which 

 it has been possible to 

 study the embryos of 

 fossil plants in detail. 

 The embryo is a typical 

 dicotyledonous one, 

 with the pointed radicle 

 directed towards the 

 micropyle. The hypo- 

 cotyl is short ; more than 

 half the whole length of 

 the embryo is occupied by 

 the two thick cotyledons, 

 the surfaces of which are in contact (see Figs. 203, C, 

 205). Between them, the growing point of the 

 plumule has been recognised in favourable prepara- 

 tions (Fig. 205, a). The tissue of the embryo is to 

 some extent preserved, and the position of the young 

 vascular bundles in the cotyledons can be determined 

 (see Fig. 203, C, which represents a seed in trans- 

 verse section, passing through the two cotyledons, ct). 

 The vascular cylinder of the hypocotyl has also been 



;. iG$.—Beiinettites Gibsoiiianits. Longi- 

 tudinal section of seed, showing dicotyle- 

 donous embryo, c, c, the two cotyledons ; 

 a, apex of plumule ; />, radicle. x 12. 

 From a photograph by Dr. Housfield. 

 S. Coll. 351. 



