THE HOMOSPOROUS LEPTOSPORANGIATJE 



391 



e. g., Alsophila contaniinans, the trunk is finite free from roots, 

 and the leaves fah away, leavini,'- very cliaracteristic scars 

 marked by the vascular Inuidles. in others, like Dicksunia aiit- 

 arctica, the whole trunk is covered with a thick mat of roots, 

 thicker than the trunk itself. 



The prothallium is exactly like that of the Polypodiaceae, 

 so far as it has been studied (Bauke ( i ) ), except that in some 

 species of Alsophila there are curious bristle-like hairs upon the 

 upper surface. In the structure of the antheridia the Cyathe- 

 aceae are intermediate in character between the Polypo(liace?e 

 and the Hymenophyllace?e. The characteristic funnel-formed 



Fig. 229. — A, Part of a sporophyll of Thyrsopteris elegans, X2; B, section of the 

 sorus, Xio; C, leaflet, with two sori, of Cyathea microphylla. (A, B, after 

 Kunze; C, after Hooker.) 



primary wall of the former occurs here, btit not until one and 

 sometimes two preliminary basal cells are cut off, as in Os- 

 munda or Hymenophylhim. The following divisions corre- 

 spond exactly with those of the antheridium of the Polypodi- 

 aceae, except that Bauke states that the cap cell, as well as the 

 upper ring cell, may divide again. The dehiscence is effected 

 either by the separation of an opercular cell or by the rupture of 

 the cap cell. The archegonia are like those of the Polypodi- 

 aceae. In Cyathea nicdullaris Bauke figures a specimen, how- 

 ever, where the neck canal cell is divided bv a membrane (1. c. 

 PL IX, Fig. 8). 



The first divisions in the embryo correspond with those of 

 the Polypodiaceae, but the further development of the young 

 sporophyte is not known. 



