Historical 1^ 



plants and insisted on the need of each species being defined by 

 morphological characters. Attention was also directed to the 

 value of the appendages as affording diagnostic characters, and the 

 various shapes and mode of branching shown by these organs 



were carefully noted. 



With respect to nomenclature, Wallroth made some unfortu- 

 nate changes. Regarding the name Erysiphc as unsuitable (on ac- 

 count of its derivation from the Greek word "^[>uai^r^, which is 

 stated to have meant robigo, or rust), Wallroth proposed Alphito- 

 morpha in its place, and used the name Erysibc to supersede the 

 genera Uredo, Ustilago, etc. These changes, however, were not 

 adopted by subsequent authors, and it need only be mentioned that 

 in accordance with the laws of botanical nomenclature, Wallroth's 

 reasons for overthrowing the name Erysiphe for the present group 



are insufficient. 



An appendix by Schlechtendal immediately followed Wall- 

 roth's paper in the Berlin Verhandl. This work is especially in- 

 teresting from the fact that it is here for the first time clearly rec- 

 ognized that t\\e Erysiphaccac may be divided into two groups, one 

 in which the perithecia contain a single ascus with eight spores, 

 the other in which these contain several asci. This important fun- 

 damental difference is well shown in a figure. 



From 1 8 19 until 1851 little advance was made. 

 In 1823 Kunze (208) founded the genus Podosphaera for the 

 '' Sphaeria myrtilUna'' of Schubert, and gave good figures illus- 

 trating the characters of the genus. 



Link, in 1824, in Willdenow's "Species Flantarum," arranged 

 the species described up to that time in two sections, "sporangi- 

 olo unico," and " sporangiolis pluribus." 



In 1825-27 Greville, in the Scottish Crj^ptogamic Flora, de- 

 scribed and figured Erysiphe pisi {= E. polygoni), E. adnnca ( 

 Uncimda salicis), and Eurotium rosarnm (= Sphaerothcca pannosa). 

 Perhaps the most important works about this time were Fries' 

 Syst. Myc. (1829), Duby's Botanicon Gallicum (1830), and Wall- 

 roth's Fl. Crypt. Germ. (1833). although they added but little to 



I of the Erysiphaceac. 

 In 1834 Schweinitz (322) published an account of the North 

 American forms, in which sixteen new species were described ; 



