Metaphyta Polytrichum. ici 



the degree of parasitism in any fungus, the more degenerate 

 are the reproductive organs. The impulse given to the 

 plant causing it to produce reproductive cells probably 

 comes from the protoplasm of the host instead of from the 

 protoplasm of a male sexual cell (Marshall Ward). When 

 surrounding conditions are such that extraneous impulse 

 cannot be obtained, then true sexual reproduction super- 

 venes and saves the parasite from extinction. 



SECTION IV. Musci POL YTR1CHUM. 



We began our study of Penicillium by emphasising the 

 salient features in its structure and life-history as popularly 

 known. Similarly, in the case of 'the moss, we will begin our 

 discussion of the type by noting certain general points which 

 at once strike the eye (fig. 31). 



First we note that the thallus, which in Fucus was a 

 flattened branched brown expansion, and in Penicillium a 

 colourless loose filamentous mass without definite form, is 

 here distinctly more in accordance with what we are com- 

 monly disposed to associate the term plant. We note the 

 existence of a distinct stem, from which leaves arise, and 

 the continuation of the stem below ground as a root. We 

 note, moreover, that the thallus has chlorophyll present in 

 its cells. Further, at certain seasons of the year we find 

 small cylindrical urns or boxes surmounted by pointed caps 

 which spring from the free termination of the thallus and are 

 separated from it by a long stalk. So far for the popular 

 knowledge of the life-history of the moss. AVe must now 

 deal more in detail with these various parts, and endeavour 

 to trace a relationship between the stages in the life-history of 

 the moss and those of the two immediately preceding types. 



Treating first of the thallus, we may for convenience of 

 description separate it into stem, root, and leaves. 



Stem. The stem of the moss presents us with an example 



