118 THE ASCOMYCETES 



phal branches that are in approximate contact bear oval oogonia 

 and slender, somewhat spirally wound antheridia. Each organ is 

 borne on a stalk cell, and each is uninucleate. After the opening 

 of their adjoining tips, the antheridial protoplast passes into the 

 oosfonium. The oojronium then elons^ates and divides into sev- 

 eral uninucleate cells, \\hich send out ascogenous hvphae. After 

 crosier formation asci are formed. In each ascus eiq;ht nuclei 

 are produced, but onlv four ascospores are formed. 



The group has been rather extensively monographed. The 

 studies of Stevens (1916, 1928) deal with Puerto Rican and Ha- 

 waiian species, those of Doidge (1920) with South African 

 species, and those of Fraser (1933, 1934, 1935, 1935a) with Aus- 

 tralian species. Theissen and Sydow (1917) divide the family 

 into 19 genera. 



Other Erysiphales. Two other families, Englerulaceae and 

 Capnodiaceae, are included by Theissen and Sydow (1917) in 

 this order. Both are sooty molds, the Englerulaceae containing 

 about 30 species of parasites on tropical plants and the Capnodi- 

 aceae 25 genera and hundreds of species that live mostly on excre- 

 tions of aphids and scale insects. 



Among the best-known species is Capnodhnn citri, causing 

 sooty mold of citrus. This fungus may be so profuse as to inter- 

 fere with photosynthesis, and the fruits must be cleansed before 

 beingr marketed. 



Scorias spongiosa occurs on beech twigs, making sponge-like 

 masses several inches in diameter. They are carbonaceous and 

 brittle when dry but pliable when moist, and can absorb and hold 

 water quite like a sponge. 



Attention has been called to the occurrence of Adelopiis 

 Qrawnavni on Doug-las fir in Switzerland and in the north- 

 eastern United States [Boyce (1940)]. This capnodiaceous 

 fungus is associated with a leaf-cast disease that may be so severe 

 as to result in the death of affected trees. 



LITERATURE CITED 



Ballard, W. S., "Apple powdery mildew and its control in the Pajoro 



Valley," U. S. Dept. Agr., Bur. Plant hid. Bull., 120. 16 pp. 1914. 

 Blodgett,'f. AI., "Hop mildew," Cornell Agr. Exp. Sta. Bull., 52^:281-310, 



1913. 



