VI, 



THE BRYALES 



225 



calyptra very large and covered with a dense growth of hairs 

 (Fig. 119, D). 



The structure of the peristome in the Polytrichacea^ is 

 entirely different from that of the other Mosses. It is com- 

 posed of bundles of thickened fibrous cells arranged in crescent 

 form, the ends of the crescent pointing up, and united with the 

 adjacent end of the bundle next it. The tops of the teeth thus 

 formed are connected by a layer of cells stretching across the 

 opening like the head of a drum. This membrane is known 

 technically as the ''Epiphragm" (Fig. 119, C). 



The Buxbaumiace^ 



The last group of Mosses to be considered is the very 

 peculiar one of the Buxbaumiaceae. In these Mosses the 



Fig. 123. — A, Protonema of Buxbaumia indusiata, with the anthreidial shoot, X175; 

 B, antheridium, seen in optical section; C, sporophyte of B. sp., X4. (A, B, after Goebel.) 



gametophyte is extraordinarily reduced, although the sporo- 

 gonium is large and well developed. So simple is the sexual 

 plant, that Goebel (i6) has concluded that these ought to be 

 taken away from the rest of the Mosses, and removed to a dis- 

 tinct order. According to Goebel's account, the antheridia, 

 which are long stalked, are borne directly upon the protonema, 

 and subtended by a single colourless bract (Fig. 123). The 

 female branches are also verv rudimentarv, but less so than the 

 male. On the strength of the extreme simplicity of these, 

 Goebel thinks that Buxhaumia is a primitive form allied to some 

 alga-like progenitor of the Mosses. There are, however, two 

 very strong objections to this. First the sporogonium, which 

 15 



