2/6 PLANT LIFE. 



shaped, or like a watch in outline. Each sporangium 

 contains some 64 spores. A strong ring of thickened 

 cells runs very nearly all round the wall of the sporan- 

 gium. This ring is elastic and in the course of its dry- 

 ing up bursts the thin wall of the case. After bending 

 backwards, it suddenly springs forward again, throwing 

 the spores to a considerable distance. In some ferns 

 the spore-bearing leaves are nearly vertical or much 

 more upright than the others, which, of course, greatly 

 increases the distance to which the spores are thrown. 



There are little hairs at the base of the sporangium 

 which probably secrete moisture and keep the cluster 

 from drying up ; and this is probably also the function 

 of the white scale or indusiuin which entirely covers 

 the clusters. 



The spores germinate in light only and produce a 

 flat green heart-shaped body, 'Olvq prothallium, on which 

 there are both male and female organs. The male or 

 antheridia produce a great number of small spirally 

 coiled antherozoids or spermatozoids each with a tuft of 

 cilia at the apex. The female or archegonia are chimney- 

 like structures with the ^^^ cell concealed at the base. 

 A drop of malic acid is secreted by the archegonium 

 and attracts the spermatozoid which eventually passes 

 down the chimney and unites with the egg-cell. 

 The latter then begins to develop into a new fern. 

 These prothallia can sometimes be found in quantity 

 on fallen logs in woods. They are independent of the 

 mother plant and have both green cells and absorbing 

 root-hairs or rhizoids. Both the male and female organs 

 are below and somewhat in front of the prothallium ; so 

 that they are to a certain extent protected. Although 

 the antherozoids swim to the archegonium, it is found 

 that a small insect, the Podura, one of the Springtails 



