114 



tive. It is probable that evolution is still going on and new 

 associations and what man calls new species are still being de- 

 veloped. 



The second method is surer. The soredia are granules con- 

 taining both fungal and algal cells borne on the thallus or 

 podetium. As the thallus and podetium mature, or regenerate 

 after drying out or weathering, soredia develop on the surfaces. 

 These gradually loosen and fall off, and may roll or be blown 

 by the wind or carried by insects or animals for some distance. 

 Timely moisture and a temperature above freezing are all they 

 need to start new colonies, which in time will develop perfect 

 lichens, bearing apothecia. Most reproduction of Cladoniae is 

 probably effected by this method. 



Fragmentation, by the drying out and breaking up of lichen 

 thalli, occurs in large foliose species, such as Parmelia, and if 

 fortunate wetting by rain or dew occurs soon after scattering 

 of such fragments, they may start new colonies, as the soredia 

 do. Occasional reproduction of Cladoniae may occur in this 

 manner. 



The genus Cladonia is divided, according to the arrangement 

 now generally used, which was adopted by Professor Edward 

 August Vainio, the distinguished Finnish authority, into three 

 subgenera: Cladina, including the "Reindeer Mosses;" Pycno- 

 thelia, with the single species C. papillaria, short, simple forms; 

 and Cenomyce, with foliaceous primary thallus, which the first 

 two subgenera lack, including a great variety of species. The 

 Latin names must be used here, for few lichens have common 

 names, and students should learn the scientific names in the 

 beginning, for with an understanding of the meanings of the 

 Latin and Greek roots, from which the specific titles were 

 framed (except in the cases of some honorific names), their fit- 

 ness and accuracy will be appreciated. The botanists of the 

 Eighteenth Century who studied lichens often showed a keen 

 appreciation of outstanding characters and some of their 

 specific names have survived for two centuries. If the student 

 is unfamiliar with Latin and Greek, the meanings of the roots 

 of the specific names may be found in such works as Jackson's 

 Botanical Dictionary. 



An interesting method of determining the precise identity 

 of a number of species of Cladonia is by the application of 



