326 Bulletin 73. 



toward the base and often are quite sharp pointed. Occasionally 

 where thej^ are not much crowded the stalk cell is considerably 

 broader, attaining a diameter quite equal to that of the ascus at 

 its distal end, while it will be broader than the lower end of the 

 ascus. The pointed ends of the stalk cells frequently intrude 

 somewhat between the cells of the epidermis. 



The number of spores in an ascus is usually eight or approx- 

 imately that number. They are rounded or oval and measure 

 3-4 in diameter. Sometimes the number is quite constantly four 

 in a large number of asci and then the diameter is considerably 

 greater, reaching 5 or 6. Asci with only four spores were found 

 by me quite frequently on specimens of peach leaves distributed 

 in Seymour and Earle's Economic Fungi, Fasc. I No. 14, and 

 collected in Temple, N. H., June 18, 1888. A few of these are 

 illustrated in fig. 21. Sadebeck* records the same variation in 

 the case of Exoascus epiphylliis , E. farlowii^ Taphrina ulmi, T. 

 bullata, and others. Brefeldf suggested that according to the 

 custom of some authors in using the number of spores as a basis 

 for the separation of genera that the four spored Exoascece should 

 be separated from the eight spored ones. Eight spored asci, 

 however, present very great variations in a number of Ascomy- 

 cetes so that in asci from the same perithecium there may be four, 

 six or eight spored asci. Several species of Teichospora may be 

 cited as examples of this. 



Prunus avium L. English Cherry. 

 Exoacus cerasi (Fuckelj Sadeb. 



This species, Exoacus cerasi (Fuckel) Sadeb. has been found on 

 "escaped cherry trees" at Germantown, Pa., by Prof. Thomas 

 Meehan. It was distributed in Ellis, N.A.F. Xo. 2286, as Exo- 

 ascus wiesneri Rathay. 



This fungus forms the well known ' ' witches brooms ' ' of Pru- 

 nus avium and P. cerasus in Europe. The mycelium is perennial 

 in the affected twigs, the fructification only showing upon the 

 leaves. In response to an inquiry' Professor Meehan writes that 



* Die parasitischen Exoasceen. Abgedruck. a. d. Jahrb. d. Hamburg. 

 Wiss. Anst. X, 2, pp. 8-9. 1S93. 



t Unters. a. d. Gesammt. d. Mykol. IX, p. 144, Miinster, 1891. 



