444 



MOSSES AND FERNS 



CHAP. 



changes in the moisture of the atmosphere. A careful study of 

 the dehiscence of the sporangium shows that as it dries the 

 expansion of the elaters assists very materially in opening it, 

 and their function is something more than that of keeping the 

 spores together, as has been asserted (Buchtien (i), p. 15). 

 The striation of the elaters is merely the result of wrinkling by 

 drying, and when moistened this disappears completely. The 

 elaters show the cellulose reaction except upon the upper surface, 

 which is cuticularised. 



The spores contain much chlorophyll, which in the dry 

 spores appears amorphous and gives them a dark olive-green 

 colour. So soon as the spore is moistened, however, it increases 



r„. 



Fig. 257. — In this and all the following figures of Equisetum, the drawings were made 

 from E. telmateia (£. maximum. Lam.), unless otherwise indicated. A, ripe, dry 

 spore with expanded elaters, Xi8o; B, a similar spore placed in water, Xi8o; C, 

 D, germinating spores, X360; E, older stages of germination, X180; r, primary 

 rhizoid. 



in diameter by about one-half through the absorption of water, 

 and the numerous small round chloroplasts then become very 

 evident. The nucleus is large, and occupies the centre of the 

 spore. After a short time the elaters and the outer layer of 

 the exposore are thrown off, and probably the rest of the ex- 

 ospore, as no trace of this can be seen in the young prothallium. 

 The spores quickly lose their power of germination, and 

 should be sown as soon as they are discharged. If this is done 

 germination begins almost at once, and within ten to twelve 

 hours the first division wall may be completed. The chloro- 

 plasts rapidly multiply by division and often show a distinct 

 radiate arrangement, extending in lines from the nucelus to the 

 periphery. The first division may occur before the spore has 



