352 XXV. REPRODUCTION OP THE BRYOPHYTA. 



of the teeth and cilia, has shrivelled up, separating from the inner 

 surface of the cilia, which extend to the top of the lid. This 

 tissue now forms on the columella only a projecting conical knob. 

 The columella is visible in its entire length ; similarly we can 

 survey the spore-sac, its outer wall, the looser tissue lying 

 between this and the wall of the capsule, and lastly this wall. 

 The spore-sac, so long as the lid has not been cast off, is closed 

 above by a thin layer of tissue. Later on, it opens by the 

 rupture of this layer. At the base of the capsule, under the 

 spore-sac, an annular cavity has been formed. The apophysis, 

 as is now seen, is provided with stomata, for on well-nigh every 

 median longitudinal section, such will be cut. They lie below 

 the level of the epidermis ; a pit leads down to each ; an air- 

 chamber adjoins it internally. It is surrounded by chlorophyll- 

 containing tissue, the intercellular spaces of which communicate 

 with the annular cavity under the spore-sac, and with the inter- 

 cellular spaces of the entire chlorophyll-containing tissue sepa- 

 rating the wall of the capsule from the spore-sac. We have here, 

 in short, an assimilating system, which enables the sporogone in 

 part, if not altogether, to effect its own nutrition. All the 

 stomata in this longitudinal section are cut in the direction of 

 their length, and give figures which, so far as can here be deter- 

 mined, agree with those of the Vascular Cryptogams, and of 

 Phanerogams. This latter is so much the more striking since 

 the apophysis (or, here and there, the wall of the capsule as well) 

 is the only place in mosses where true stomata, constructed after 

 the type of the higher plants, are borne. 



In order to complete the impression we have obtained, let 

 us now examine surface-sections of the capsule and of the 

 apophysis. We can decide that on the surface of the capsule, 

 stomata are wanting ; between the brown-walled cells of the 

 apophysis we see, however, pits which lead to the stomata. If 

 we turn the section over, and examine it from the inner side, 

 we can in favourable cases distinguish the two guard-cells of 

 the stomata, formed as in higher plants. Upon such sections we 

 can at the same time determine that the green cells, between the 

 wall of the capsule and the spore-sac, are joined together in longi- 

 tudinal series, that they are branched, and have all the aspect 

 of algal threads. On cross-sections through the apophysis sto- 

 mata have usually been cut, the two guard-cells of which are not 

 difficult to see. At the seta, the differentiation of the epidermis 



