MiCROSPHAERA 121 



MICROSPHAERA Lev. Ann. sci. nat. III. 15: 1 54, sub Gz/^- 



cladia, & 381. 185 I 



Perithecia globose to globose-depressed : asci sev^eral, 2-^- 

 spored. Appendages not interwoven with the mycehum, branched 

 in a definite manner at the apex, which is usually sev^eral times 

 dichotomously divided, and often very ornate, rarely {M, astra- 

 gtili) undivided or once dichotomous. Etym. lUKpoi:, parvus^ and 

 Oifacpa^ sphaera. 



Distribution, — Europe, Asia, and North America ; 1 3 species 

 and 6 varieties. 



As a rule, the genus Microsphaera is easily known by the 

 much-divided and ornate apex of the appendages. In one species, 

 however, JZ astragali, the appendages are very frequently un- 

 branched at the apex, and through this species Microspliacra ap- 

 proaches the genus Etysiphe. From all species of Erysiphc, how- 

 ever, M. astragali is distinct in the long, white, assurgent, fascic- 

 ulate appendages. In E. tortUis, where the habit is somewhat 

 similar, the appendages are brown. At first sight it seems unnat- 

 ural to separate in different genera these two species, and some 

 authors have preferred to place M. astragali in the genus Erysiphc. 

 Apart from the fact, however, that the apex of the appendages in 

 J/, astragali is sometimes definitely branched in a dichotomous 

 manner (so making the view possible that the unbranched condi- 

 tion is to be considered merely as the result of immaturity), this 

 species is evidently too closely allied to M. Bixumlcri to be sepa- 

 rated generically from it ; while E. tortilis is similarly very close to 

 certain forms of E. polygoni. Magnus (231, p. 150) has lately 

 proposed that the characters of the two genera Microsphaera and 

 Erysiphe should be emended, but the definitions proposed by this 

 author (which involve the transference of E. tortilis to the genus 

 Microsphaera) seem to me to be less natural than that which gives 

 the strictly apical branching of Microsphaera as the difference of 

 chief generic importance. Magnus (/. c) speaks of angularly bent 

 appendages as being distinctive of the genus Erysiphe ; this char- 

 acter, as separating the two genera, would, howe\-er, break down 

 in M. euphorbiac and in many forms of E. commums. 



I have not seen sufficiently mature examples of M. umbilici on 

 Cotyledon {Umbilicus) Semenovii and M. ferruginea on Verbena 



