4 INTRODUCTION 



range and occur in the temperate regions of Europe and America; hut very much 

 thr larger number of these, including all of the Marattiaceae, are tropical or sub- 

 tropical plants and are very seldom seen in cultivation, hence material for their 

 study must be collected in their natural habitat. 



I he gametophytes, or sexual plants, are seldom encountered unless very 

 special search is made foi them, and they have been but rarely collected; and even 

 where the spores can be made to germinate, the long time necessary for the growth 

 of the gametophyte under artificial conditions, and the difficulties of rearing them 

 to maturity, readily explain the small number of successful attempts to study these 

 plants under artificial conditions. 



As the result of several visits to the tropics of both the Old and New Worlds, 

 the writer has collected material of all of the eusporangiate genera, except the 

 recently discovered Archangiopteris from southwestern China and Macroglossum 

 from Borneo. It has seemed desirable, with this material as a basis, to make a some- 

 what comprehensive comparative study oi the whole group of the Eusporangiatae. 

 In this study, especial attention will be devoted to the sn ucture and development of 

 the gametophyte and embryo and to the development of the young vegetative organs 

 of the sporophyte. The general anatomy and histology of the mature sporophyte 

 have already been pretty satisfactorily studied and described for most of the genera 

 and a particularly satisfactory account of the development of the sporangium has 

 been given us in the comprehensive memoirs of Professor Bower (Bower 5, 6), and a 

 detailed investigation of these points has hardly seemed necessary, although, so far 

 as possible, the results of the work of previous investigators have been verified. 



The writer has already published various papers upon the development of 

 both the Marattiaceae and Ophioglossaceae, and these have been freely drawn upon 

 in the preparation of the present monograph; but these earlier studies have been 

 materially extended by further work upon the species previously studied and in- 

 vestigations have been made upon a number of species which hitherto have not 

 been examined at all, or have been studied only very incompletely. This is partic- 

 ularly true of the genus Danaa, which has received comparatively little attention 

 hitherto. An especially fine lot of material of several species of Daniea was col- 

 lected in Jamaica in 1908 and an extended study of the gametophyte and young 

 sporophyte has been made, the complete results of which are now published for 

 the first time. Attention has also been given to the development of the young 

 sporophyte in the other eusporangiates, particularly in the peculiar genus Kaul- 

 fussia, which, like Danaa, has received less attention from the students of these 

 plants than have the genera Marattia and Angioptcris. 



( )f late there has been a tendency, especially among students of the fossil ferns, 

 to lay great stress upon the importance of the structure of the vascular skeleton of 

 the ferns in the study of their phylogeny. It is therefore highly important that a 

 careful examination should be made of the origin and development of the vascular 

 system in those forms, i. e., the Eusporangiatae, which, there is good reason to sup- 

 pose, are the nearest relations among living plants of the ancient Paleozoic ferns. 



The results of the writer's studies on the development of the fibro-vascular 

 bundles of the sporophyte in all of the eusporangiate ferns have led to some rathei 

 unexpected conclusions as to the real nature of the vascular system in these ferns, 

 conclusions decidedly at variance with the views generally accepted at present. 

 These results have seemed sufficiently important to warrant a more extended treat- 

 ment of this subject than was at first contemplated; and this will explain what 

 might otherwise seem to be a disproportionate amount of space devoted to the origin 

 and development of the fibro-vascular system in the young sporophyte. 



