EIJSHA MlTrnP:LL SCIENTIFIC SOCIETY. 03 



pierce through the epidermis of their host. The eoiiidial stage 

 consists of short branches arising perpendicularly to the weft, 

 of mycelium which abjoint serially oval or oblong conidia, which 

 in numbers give a powdery appearance to the mildew. 



The mature condition of the fungus is manifested to the 

 unaided eye in the form of minute concoptaeles of a dark color, 

 which can be seen here and there to dot the surfacie of the leaf, 

 sometimes vavy numerous and quite evenly distributed, or again 

 loosely aggregated or very few in number. 



It is outside the purpose of this paper to describe the rather 

 complex development of these conceptacles which result from 

 sexual organs. With proper magnification they are seen to be 

 of a blackish, or various shades of a brown, color, the surface being 

 more or less definitely reticidated, and in a single plane of the 

 periphery they have a number of filamentous appendages of 

 various forms of development, either hyaline or colored. The 

 interior of a conceptacle, or peritkeclam, is occupied with one or 

 several sacs, or ascl, which themselves contain a variable num- 

 ber, two to eight, of one-celled spores. 



It is a source of regret to myself that a greater number of 

 species have not been collected, and the absence of some common 

 ones will be noticed. In a number of cases the conidial stage of 

 Erysi'phe graminis and Sphcerotheca paiinosa have been very 

 abundant, but I have not collected the fruit in the past four years. 



During the past year the conidial stage of Sphoerotheca pan- 

 nosa has l)een very injurious to roses in Auburn, Ala. 



The measurements are given in terms of the micromillemeter. 



To serve in distinguishing the genera the following "brief key 

 will be found serviceable: 



I. Appendages simple. 



a, Irregularly fiexiions. • 



1 , One ascus — Sphoerotheca. 



2, Several asci — Erysiphe. 



b, Coiled at the tips — Uncinula. 



c, Needle-shaped, swollen at base — Phyllaclinia. 



II. Appendages dichotoinously branched. 



a, One ascus — Podosphcera. 



b, Several asci — Microsphcera. 



III. Appendages percurrent, primary branching opposite — Microsphcera. 



