MiCROSPHAERA 155 



branching of a very different type to that of M. alni ; the branch- 

 ing being very lax and irregular, with straight tips to the ultimate 

 branches (Figs. 27, 29). 



In the latter case there is much resemblance to M. diffusa, 

 but in that species we find the ultimate divisions (of the mature 

 apex) forming long, rather slender, nearly parallel branches. 

 These long ultimate branches are characteristic of M. diffHsa^^.\\A 



are not found in the present plant, in which, moreover, as men- 

 tioned above, we frequently find some appendages with recurv^ed 

 tips, another character which never occurs in M. diffusa. 



The appendages of the present plant are usually angularly 

 bent, or even more or less contorted ; this character together with 

 that of the great variability in the apical branching, give much the 

 appearance of a "sport" ; but as the plant has been collected in 

 three different localities on different host plants, it can hardly be 



dismissed as this. 



M, cupJiorbiae has the same curiously contorted appendages, 

 but differs in the longer appendages, with very flexuous apical 



■ 



branching, etc. If we consider the bent appendages as a character 

 of the first importance, the present plant should rank as a variety 

 of M. eiiphorbiac rather than of M. alni ; but it is possible that 

 the more or less contorted growth of the appendages is due, in 

 the present case, merely to the great crowding of the perithecia 

 and the consequent interlacing of their appendages. Moreover, 

 in some perithecia the appendages are nearly or quite straight ; 

 this is, however, very exceptional. 



. Except in the very variable nature of the apical branching, and 

 the contorted appendages, the present plant does not differ from 



M. abii. 



The usually very lax and irregular apical branching certainly 

 separates the present plant widely from the ordinarj^ forms of M. 

 alni, and it is only the occasional occurrence of appendages with 

 recurved tips and a closer t>^pe of branching that has led to its 

 being placed, with some hesitation, as a new variety under 3L 



alni. 



It may be well here to review the position of these six vari- 

 eties of M. alni. In America we have the four varieties extcnsa, 

 calodadophora, vaccinii, and liidcns. The position of these to the 

 type may be stated as follows : 



