238 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Over one hundred thirty species are known. Some are impor- 

 tant parasites. 



Conidial forms are found in Phoma and Phyllosticta. 



G. bidwellii (E.) V. & R.^- ^*^"^ 



Perithecia minute, globose, subepidermal, erumpent, perforate; 

 asci clavate-cylindric, obtuse, 60-70 x 10-13 fi; spores elliptic to 

 oblong, continuous, 12-17 x 43^-5 fi. 



Conidia (= Phoma uvicola, Phyllosticta labruscae, Naemospora 

 ampeUcida) borne in pycnidia 180 x 180 fi, subepidermal, elliptic, 



Fig. 173. — Diagrammatic section of a perithecium con- 

 taining ascospores. Germination of a spore at the 

 right. After Reddick. 



thick-walled; conidiophores short, simple; conidia ovate to elliptic, 

 8-10 X 7-8 /J.. FiUform microconidia ("spermatia") are borne in 

 flask-shaped pycnidia 0.1-0.2 x 0.45-0.46 fi. 



The fungus has been placed successively in the genera Sphseria, 

 Physalospora, Laestadia and Guignardia. 



An extensive synonomy is given by E. Rose ^^' who concludes 

 that the name should be G. ampelicida. 



It is found on all green parts of Vitis and Ampelopsis, the as- 

 cigerous stage common only on the mummified fruits. 



Perithecia were first found in 1880 by Dr. Bidwell in New Jersey; 

 They are abundant on berries, which have wintered out doors. 



Reddick admirably describes the" development of the spots as 

 follows: 



