6 4 8 STUDIES IN FOSSIL BOTANY 



(p. 586). The sporophylls, so little differentiated from 

 the vegetative foliage, may best be compared with the 

 stamens of Bennettiteae on the one hand, or with the 

 foliaceous carpels of Cycas on the other. 



The question whether the Lyginodendreae or the 

 Medulloseae were the nearer to the main line of 

 Cycadean evolution may be a sterile one, for there 

 were doubtless many other races of Pteridosperms, 

 among which the true ancestry may lie concealed. 

 A few points of comparison may, however, be noted. 

 So far as the anatomy of the stem is concerned, 

 Lyginodendron appears to come near the Cycads, for 

 the general organisation is of a similar character, and 

 the mesarch structure of the bundles is still retained in 

 the peduncles of the cones of some recent Cycads as 

 well as in the leaves (p. 364). The habit and anatomy 

 of the Lyginodendron foliage is, however, unlike anything 

 known either in Mesozoic or recent Cycadophyta. 1 It 

 has been suggested that Lagenostoma, the seed of 

 Lyginodendron, may have given rise to the seed of 

 Cycadaceae by the cupule becoming adherent to the 

 integument, and thus constituting the supposed outer 

 integument of the Cycadean ovule. 2 This view, 

 however, assumes that the integument of the seed in 

 recent Cycads is double, an interpretation which is 

 still open to much doubt. 



1 It is conceivable that a reduction of a leaf of the Sphenopteris type 

 might lead to a structure not unlike that of the leaf in the genus Cycas, with 

 uninervate pinnae. The very curious Annam species, C. Micholitzii, Dyer, 

 with quadrifid pinnse, is of interest from this point of view. See Gardener's 

 Chronicle, August 19, 1905. 



2 MissM. C. Stopes, "Beitragez. Kenntnis der Fortpflanzungsorgane der 

 Cycadeen," Flora, Bd. xciii. 1904 ; " On the Double Nature of the Cycadean 

 Integument," Ann. of Bot. vol. xix. 1905. 



