26o ROMANCE OF LOW LIFE AMONGST PLANTS. 



within the stems during the winter ; so that the old 

 stems of plants, which are infested with the mould 

 during the autumn, conceal within themselves, during 

 the winter, a large number of these " resting spores." 

 As the old stems rot and decay, the resting spores 

 are set free in the spring, and then a period of activity 

 commences. The contents of these globose bodies 

 become differentiated into a large number of zoo- 

 spores, which ultimately escape by a rupture of the 

 thick envelope, armed with vibratile cilia, and in all 

 respects like the zoospores which are developed from 

 the conidia. These active zoospores swarm over the 

 damp soil, and are carried by the spring rains into 

 proximity with the young seedling leaves of the new 

 crop of host plants, then the cilia are absorbed, 

 germination commences, the delicate threads of the 

 mycelium enter the nearest stomata, and infection 

 results. In this way, in addition to the spread of the 

 infection from conidia in summer and autumn, pro- 

 vision is made for an attack upon seedlings in the 

 spring. It will be inferred that, in order to check 

 the spread of these diseases, the conidia must be 

 destroyed in the autumn to prevent their extension 

 to healthy plants, and the destruction of all rotting 

 debris must be carried out during the winter so as to 

 extirpate all the concealed resting spores, and thus 

 prevent the infection of seedlings in the spring. 

 Thus it will be noted that knowledge of the life- 

 history of these parasites will suggest the best 

 methods to be employed in their destruction. It is 

 somewhat peculiar that the moulds in this group, 

 when they attack living plants, are rapid in their 



