264 



Scientific Proceedings, Royal Dublin Society. 



are numerous perforations. This condition is a very much more advanced one 

 than that found in 1'aenitis. The leaf-trace is formed by the passage outwards 

 of two meristeles. These afterwards fuse to form a single bundle in the mid- 

 rib before the venation of the leaf is begun. 



The Sorus. 



It has been already noted that the leaves of Drymoglosmm are dimorphic, 

 the sterile leaves being ovate while the fertile are linear, and approximately 

 three times the length of the sterile. 



The sori are also linear, and are somewhat sunken and parallel, one 

 running on each side of the midrib about midway to the margin. Interrup- 

 tions may occur in the sorus. There is no indusium, but the sporangia are 



Fio. 7. — Drymoglosmm carnosum. 

 (n) Scale from sorus. (b) Scale from rhizome. 



completely covered by a thick felting of scales. These scales are similar in 

 form to those found on the stem, but they are smaller (Fig. 7, h). 



The sporangia are smaller than those seen in Tacnitis, there being only 

 thirteen or fourteen indurated cells in the annulus. Sterile hairs are not 

 present. The annulus is a vertical one, and there is a large, very prominent 

 stomium of six cells. The stalk of the sporangium is three-celled. The spores 

 are two-sided. 



Venation. 



It will be remembered that the venation in Taenitis showed a well- 

 developed reticulum, with no blind endings. Fig. 8, a shows that in the sterile 

 leaves of Drymoglossum, on the other hand, intra-areolar blind-endings are 



