CHAP. XIII 



EQUISETINEA^: 



423 



except on the expanded ends. They are extremely hygroscopic, 

 and respond instantly to any changes in the moisture of the 

 atmosphere. A careful study of the dehiscence of the spor- 

 angium shows that as it dries the expansion of the clatcrs 

 assists very materially in opening it, and their function is 

 something more than that of keeping the spores together, as 

 has been asserted.^ The striation of the elaters is merely the 

 result of wrinkling by drying, and when moistened this dis- 

 appears 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 



Fig. 218. — In this and all the following figures of Equisetnm, the drawings were made from E. tel- 

 iiiateia (Ehrh.), {E. ma-vimuvi, Lam.), unless otherwise indicated. A, ripe dry spore with 

 expanded elaters, x 180 ; B, a similar spore placed in water, X180; C, D, germinating spores, 

 X360 ; E, older stages of germination, X 180 ; 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 exospore are thrown off, and probably the rest of the 

 exospore, 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 



•^ Buchtien (i), p. 15. 



