200 MISCELLANEOUS EXAMPLES 



sometimes abundantly and sometimes sparsely : while examination 

 of these or other leaves under the microscope will often show an 

 abundance of the early stages of such bright green specks, so 

 minute as to have been invisible with the mere hand lens. 



It is best to pick out the smaller leaves for microscopical 

 examination, and even then (especially with L. gibba) the examina- 

 tion can often only be satisfactorily carried out by placing one of 

 the leaves in a drop of water on an excavated glass slip (taking 

 care that its upper surface is uppermost) and gently compressing 

 the leaf, if necessary, with the cover-glass. 



An examination of a very large number of these infected leaves 

 has enabled me to ascertain the following facts. 



The very active spores of the Chlorochytrium penetrate to some 

 of the intercellular spaces of the leaf through the stomata. Single 

 spores, or such bodies after a primary fission, may be seen just 

 within the stomata. Sometimes the entire spore, or the segments 

 of the once or twice divided spore, will grow considerably before 

 undergoing any further fission though, more commonly, division 

 goes on so as to produce eight or more cells which, as they grow, 

 soon become tightly packed within the now dilated sub-stomatal 

 space. Examination of the surface of the leaf over one of these 

 patches will always reveal a stoma greatly dilate'd and almost 

 circular in shape. 



The mode of infection in L. minor and L. gibba is, therefore, 

 altogether different from that described by Cohn as occurring in 

 L. trisulca. In that species of Duckweed there is curiously enough 

 an absence of stomata. The average shape and appearance of the 

 patches of Chlorochytrium in it is also rather different from that 

 of the patches in the other two Duckweeds ; and the patches in 

 the latter likewise lack the distinct, and often thick, bounding 

 membrane which occurs round the patches in L. trisulca. 



In each of the forms the tendency is to an ultimate production 

 of minute spherical or ovoidal zoospores, which, after exhibiting a 

 swarming movement, may make their way out of the space where 

 they have been developed. It often happens, however, in each of 

 these forms of Chlorochytrium, that the zoospores may, either in 

 whole or in part, not succeed in escaping, but come to rest within 

 their respective cells or spaces. 



Multitudes of partially empty spaces may be seen containing 

 large or small specimens of the intermediate fission products, those 

 within the same space being either all of one size (Fig. 28, C, 



