328 The Botanical Gazette. [December, 



paratively modern, specialized group, comparable to the leafy 

 liverworts or the true mosses. There is no geological evidence 

 to show that the true leptosporangiate ferns were ever much 

 more numerous or better developed than at the present time. 

 On the other hand, the geological record, as well as embryo- 

 logical study, so far as the latter has been applied to them, 

 points to the primitive nature of the Eusporangiatae. 



The most recent and careful study of the carboniferous and 

 pre-carboniferous ferns, show that their affinities were not 

 with the Leptosporangiatae, but with the Eusporangiatae, 

 especially the Marattiaceae. Forms probably referable to the 

 Ophioglosseas, and probably also to the Osmundaceae, 1 have 

 also been found, but no unmistakable leptosporangiate remains 

 are known until the early Mesozoic formations, from which time 

 they increase rapidly in number and variety. Solms-Lau- 

 bach 3 justly remarks that if such forms did exist in the earlier 

 formations.it is exceedingly strange that, among the innumer- 

 able perfectly preserved leaves, a structure so durable as the 

 annulus of the sporangium should have failed to be preserved 

 in a recognizable condition. 



The ontogeny of the Kusporangiates, so far as known, har- 

 monizes with the geological evidence. The prothallium is 

 more massive, and longer-lived than in the leptosporangiates, 

 in this respect approaching the liverworts, and the sexual or- 

 gans show points of primitive structure. Unfortunately the 

 embryogeny is scarcely at all known in any of the homospor- 

 ous forms, which are presumably the most primitive and 

 approach most nearly the ancestral type. 



From a series of investigations recently completed by the 

 writer, it appears that the Osmundaceae are about midway be- 

 tween the true Eusporangiatae and the Leptosporangiatae, both 

 in regard to the prothallium and the embryo. The intermed- 

 iate character of the tissues of the sporophyte has already been 

 repeatedly called attention to by various writers. The pro- 

 thallium resembles to a remarkable degree that of certain liver- 

 worts, notably Dendroceros, and the sexual organs approach 

 in certain respects the Marattiaceae, but also recall Equise- 

 tum and even certain bryophytes. The embryo is noticeable 

 on account of the large size of the foot and its long depend- 



\ Solms-Laubach: Palaeophytologie, p. 156. 

 » Bower: Annals of Botany, May, 1891 

 8 L. c, p. 156. 



