362 MOSSES AND FERNS 



CHAP. 



like the stem (Bower (n), Klein (2)), and the young leaf is 

 more conical than in the Polypodiaceae. In the very young 

 leaf, according to Bower, one side of the apical cell is always 

 directed toward the stem apex, and never one of the angles. 

 In the presence of a three-sided apical cell, as well as its more 

 cylindrical form, there is an approach to Botrychium. The 

 further development of the leaf is like that of the pinnate leaves 

 of the Marattiaceae or Polypodiaceae, with which they agree 

 also in the strongly circinate vernation. The leaves are always 

 pinnately divided, and are similar in all the species, and the type 

 of venation is the same. While in all species of Osmunda and 

 in Todea barbara, the structure of the leaf is quite like that of 

 Polypodiacese, the other species of Todea (Leptopteris) have 

 the lamina of the leaf reduced to two or three layers of cells, and 

 there are no stomata. The texture of the leaves in these forms 

 is filmy, like that of Hymenophyllum. 



The petiole is traversed by a single large vascular bundle, 

 which in section is crescent-shaped and in structure concentric, 

 with the elements like those of the Polypodiaceae, but the enclo 

 dermis is not so clearly differentiated; and close to the inner 

 side of the bundle are numerous mucilage cells, recalling the 

 tannin ducts of Angiopteris. A further point of resemblance 

 to the Marattiaceae is the presence of stipular wings at the base 

 of the petiole. The chaffy scales (paleae) so common in the 

 Polypodiaceae are quite wanting, but hairs are developed, often 

 in great numbers. Thus in O. cinnamomea the young leaves 

 are covered completely with a felted mass, of hairs, recalling 

 those in some of the Cyatheaceae. Some of these are gland- 

 ular. The sterile leaves and sporophylls are either very much 

 alike, as in Todea, or the sporophylls may be very different. 

 An extreme case is seen in O. cinnamomea, where the whole 

 sporophyll is devoted to the development of sporangia. In 

 this species, as well as O. Claytoniana, the sporophylls develop 

 first and form a group in the centre of a circle of sterile leaves. 

 In O. cinnamomea the sporophylls develop no mesophyll, and 

 die as soon as the spores are scattered. 



The Root 



The roots of the mature sporophyte differ very markedly 

 from those of the other Leptosporangiatae, and have been the 



