392 Illinois State Laboratory of Natural History. 



literature of the family is unusually large and extended; and 

 arising from so many independent sources, and representing 

 such widely different views, there is so much confusion of 

 names and descriptions that the difficulty of study is increased 

 rather than lessened by its abundance. The plants form a 

 natural, closely related, and easily recognized group; but its rank 

 and position in the natural system has been very differently 

 estimated by different writers. 



They were known to Linnseus under the common name of 

 Mucor erysiphe. Persoon (Syn. Fung., p. 124) called them all 

 Sclerotiiim erysiphe^ but separated as a variety the form on 

 Coryhis^ now classed in the genus Pliyllactinia. Soon writers 

 began to distinguish different species, but referred them all to 

 a single genus called Erysibe by Link and Rabenhorst, Alphit- 

 omorpha by Wallroth and Schlectendal, and Erysiphe by Hed- 

 wig, the latter followed by De CandoUe, Schweinitz, Fries, and 

 others. This genus was often classed among the puff-balls, 

 (Gasteromycetes). In 1851 Leveille published a monograph of 

 the group (Ann. Sci. Nat., Ser. III., Tome XV.) in which he 

 divided the old genus Erysiphe into six genera as follows: — 



Sphwroetheca. — Perithecium containing a single ascus, 

 appendages floccose, undivided. 



Podosphwra. — Perithecium containing a single ascus, 

 appendages dichotomously divided at the tip. 



Uncinula. — Asci several, appendages coiled at the tip. 



PhijUactinia. — Asci several, appendages straight, rigid, 

 swollen at base. 



Microsphcera. — Asci several, appendages dichotomously 

 divided. 



Erysiphe. — Asci several, appendages floccose, undivided. 



Tulasne (Select. Fung. Carp. Vol. I., [1861]) does not 

 adopt this division, but returns all the species to the genus 

 Erysiphe. De Bary (Morph. und Phys. der Pilze III. [1870]) 

 divides the group into two genera according to the characters 

 of the carpogonuim, calling those Podosphaira in which this 

 organ is straight (orthotropus) and which develop only one 

 ascus, and retaining the name Erysiphe for those with a curved 

 ( campy lotropus) carpogonium and several asci. For a true. 



