BRYALES 



281 



No accurate statements are to hand showing the genetic relation of the 

 endothecium to this central tract, but it certainly gives rise to the greater 

 part, if not exclusively to the whole, of the conducting strand. 



In the upper region assimilating tissue is usually developed in more 

 or less close relation to the capsule itself, together with numerous and 

 often large intercellular air-spaces. These developments are derived chiefly 

 from the amphithecium, while at the same time the sterile cells of the 

 columella usually expand, as a tissue for water-storage : this may also 

 contain some chlorophyll, and occasionally forms air-spaces. The swollen 

 shape of the capsule is chiefly 

 due to these changes, which are 

 obviously secondary. Different 

 types may be distinguished 

 according as the assimilatory 

 system is developed from the 

 wall of the capsule itself, or 

 partly here and partly in the 

 apophysis below, or entirely in 

 the region of the apophysis. 

 For instance, in Bartramia the 

 assimilatory system is chiefly in 

 the wall of the capsule, where 

 it is equally developed all round. 

 In Buxbawnia (Fig. 137, 8, 9) the 

 same is the case, except that 

 the development is dorsiventral : 

 the capsule early takes an oblique 

 position, and the assimilatory 

 tissue is developed more strongly 

 on the better-lighted side. In 

 other cases, however, the assimi- 

 latory system extends some dis- 

 tance below the actual capsule, 



constituting the swollen region of the apophysis : this is of small size in 

 Polytrtchum, and the assimilatory system is chiefly here also in the wall 

 of the capsule, but it extends downwards to the small apophysis, while the 

 numerous stomata lie in the narrow neck between these parts. In many 

 Mosses, again, the apophysis itself becomes the chief seat of assimilation, 

 as, for instance, in Funaria (Fig. 137, 5), and this leads to its enlargement: 

 so much so that it becomes the most prominent feature in the whole 

 sporogonium : thus in the Splachnaceae it is commonly larger than the 

 capsule which it is to nourish, and in S. hi ten in (Fig. 138) it appears as 

 a wide umbrella-like expansion, which shows a structure not unlike a 

 leaf-lamina, with well-marked epidermis, spongy mesophyll, and stomata 

 upon the upper surface. Still, with all these variants at or near to the 



Splachnum hiteitin. I. Capsule open. A = apophysis. 

 II. Unopened capsule in longitudinal section. j=seta; 

 /.r = leptoxylem ; j^ = stomata on apophysis; c/=colu- 

 mella ; / = peristome ; v-f. = archesporium ; /= intercellular 

 space. III. and IV. Diagrams to illustrate the opening 

 of the capsule. (From Goebel, after Hedwis;, Vaizey, and 

 Bryhn.) 



