XI THE HOMOSPOROUS LEPTOSPORANGIAT.^ 373 



both hemispheres, and some of them, e.g. Dicksoiiia antarctica, 

 are also found in the extra -tropical regions of the southern 

 hemisphere. They correspond so closely in all respects with 

 the typical Polypodiaceae that, except for the slightly different 

 annulus, they might be placed in that family. In some forms, 

 e.g. AlsopJiila contaniinans, the trunk is quite free from roots, 

 and the leaves fall away, leaving very characteristic scars marked 

 by the vascular bundles. In others, like Dicksonia antarctica, 

 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,^ except that in some species of 

 AlsopJiila there are curious bristle-like hairs upon the upper 

 surface. In the structure of the arttheridia the Cyatheaceae are 

 intermediate in character between the Polypodiaceae and the 

 Hymenophyllaceae. The characteristic funnel-formed primary 

 wall of the former occurs here, but not until one and sometimes 

 two preliminary basal cells are cut off, as in Osniunda or 

 HyDienophylliuii. The following divisions correspond exactly 

 with those of the antheridium of the Polypodiacea;, 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 separa- 

 tion of an opercular cell or by the rupture of the cap cell. The 

 archegonia are like those of the Polypodiaceae. In CyatJiea 

 niedidlaris Bauke figures a specimen, however, where the neck 

 canal cell is divided by a membrane.' 



The first divisions in the embryo correspond with those of 

 the Polypodiaceae, but the further development of the young 

 sporophyte is not known. 



The position of the sori is that of the typical Polypodi- 

 aceae, and sometimes a decidedly elevated placenta is present. 

 The indusium is either cup -shaped {Cyathea, AlsopJiila) or 

 bivalve, e.g. Ciboiiuvi (Fig. 193). In the latter the outer valve 

 fits closely over the other like the cover of a box. The 

 sporan'gia, which are either long or short-stalked, although their 

 development has not been followed, correspond so closely in the 

 mature state to those of the Polypodiaceae that there is little 

 doubt that their development is much the same. The annulus 

 is nearly or quite complete, but above the stomium in Cibotiiun 

 Menziesii the cells of the annulus are broader but thinner-walled 



1 Bauke (I). 2 Kjiiike, I.e. PI. IX. Fig. 8. 



