284 



PART III. THE CLASSIFICATION OF PLANTS. 



while the internal portion, after rapid mitotic nuclear division, 

 separates into cells each of which secretes a proper wall and be- 

 comes a spore. In most forms a portion of the internal protoplasm 

 goes to form a number of filaments, generally tubular, either free 

 or connected into a net- work, which constitute the capillitium. 

 The wall dries, and eventually ruptures, and the spores are 

 scattered by the expansion and hygroscopic movements of the 

 elastic capillitium. In many cases the sporangium has a stalk, 



i\ 



FIG. 199. A Part of a plasmodium of IKdymium leucopus ( x 300). B A closed sporanginm 

 of Arcyria incarnata. C The same after the rupture of its wall (p) and expansion of the 

 capillitium cp (x 20). (After Sachs.) 



(sporophore) which is sometimes continued into the cavity of the 

 sporangium as a columeUa. 



In the Exosporeae the spores are not formed in the interior of 

 a sporangium, but by abstriction from the ends of filaments de- 

 veloped from the surface of the sporophore. 



In some forms (e.g. Fuligo varians) a compound sporangium is 

 formed, termed ^Ethalium, by the combination of a number of 

 plasmodia. 



