214 D- H. Scott. 



find a remarkable analogy in the corresponding fructifications of the 

 Mesozoic Bennettiteae, discovered by Dr. Wieland. The sporophylls, 

 so little differentiated from the vegetative leaves, are best compared 

 with the microsporangiate sporophylls of Bennettiteae on the one hand 

 or with the carpels of Cycas on the other. It is unnecessary to 

 further emphasize the affinity with Cycadophyta, which all characters 

 unite in establishing. When we come to details, however, and aim at 

 distinguishing the particular line of Pteridospermeae which probably 

 led on to the Cycads, the question becomes exceedingly difficult, if 

 not insoluble. So far as the anatomy of the stem is concerned, Lygino- 

 dendron appears to come near tlie Cycads, and the attempt has further 

 been made to show how the seed, Logenosfoma, might have given rise 

 to Cycadean seeds, the cupule becoming adherent and constituting 

 the supposed outer integument of the Cycadean ovule. ^) It is, however, 

 improbable that any such near relation exists. There is no satis- 

 factory^ proof of the presence of a second integument in Cycadean 

 seeds, and the hypothesis of an adherent cupule therefore appears 

 superfluous. As regards anatomical evidence, though the stem of 

 Lyginodendron is readily comparable with that of a Cycad, the petiolar 

 structure is totally different. The Medulloseae (Neuropterideae) have 

 also been regarded as nearly allied to the Cycads, a view which has 

 been vigorously maintained by Mr. Worsdell on anatomical grounds. 

 It would take far too much space to discuss this part of the question 

 in detail. In spite of the interesting points which Mr. "Worsdell 

 and M. Matte have brought forward, the evidence for the monostelic 

 nature of the Cycadean stem seems to me to be unshaken and I cannot 

 regard its derivation from a dialystelic Medullosean type as probable. 

 The strongest argument is that based on the structure of the petiole, 

 which in 3IeduUosa undoubtedly approaches Cycadean structure very 

 nearly, and may fairly be regarded as evidence of affinity. 



The Neuropteridean seed, represented by Trigonocarpon oliime- 

 forme, appears to have a good deal in common with that of recent 

 Cycads, as shown by the differentiation of the testa into a sarcotesta 

 and a sclerotesta, the double vascular system, and the form of the 

 pollen-chamber. The great difterence consists in the fact that in 

 Trigonocarpon the nucellus appears to have been free, and that the 

 internal bundle-system belongs to the nucellus and not to the inte- 

 gument. These difficulties do not seem to be insurmountable. When the 

 nucellus once became adherent to the integument the boundary between 

 the two would soon be obliterated, and a bundle-system belonging 



■) M. C. s topes. Beiträge zur Keuntuis der Fortpflanzungsorgane der Cycadeen. 

 Flora. Bd. 93. 1904; Ou the Double Nature of the Cycadean Integunieut, Ann. of Bot., 

 Vol. XIX. 1905. 



