124 



STRUCTURAL BOTANY 



are already formed. The calyptra, which was previously 

 ruptured, is now left behind as a torn membrane at 

 the base of the stalk. 



The spores of Pellia present a peculiarity which is 

 quite exceptional among Liverworts, for they become 

 multicellular while still enclosed in the capsule. In Fig. 

 57 the oval spores are shown at various stages of cell- 

 division ; when 

 ripe they consist 

 of several tiers of 

 cells. They con- 

 tain chlorophyll, 

 and continue their 

 germination,under 

 favourable con- 

 ditions, as soon as 

 shed. A wedge- 

 shaped cell, such 

 as is shown in Fig. 

 57 in the lower 

 spore on the left, 



FIG. 57. -Spores and elaters from an almost ripe becomes the 



capsule of Pellia. The spores (sp. ) are dividing growing-point of 



into numerous cells. At sp., a stage of division , , , 



is shown, el, el, elaters. Magnified 360. (R. S.) tne new P lant > 



while one or both 



ends grow out into the first root-hairs. The elaters are 

 of use in loosening the mass of spores, so that they are 

 more easily scattered by the wind. They also perform 

 hygrometric movements, which actively disperse the 

 spores. The development of the fruit of Pellia occupies 

 a full year ; when the spores are shed new archegonia 

 are already ripe for fertilisation. 



