274 



THE FUNGI WHICH CAUSE PLANT DISEASE 



Fig. 203. — G. tubifor- 

 mis, peiithecia. After 

 Winter. 



apically thickened and opening by a pore; 

 spore elliptic, 1-celled, hyaline; paraphyses 

 none. 



This genus of some twenty-five species 

 contains G. tubiformis (Tode) Sacc. which 

 is said to be the ascigerous stage of Lepto- 

 thyrium alneum Sacc. growing on Alder. 



Two other species, G. fimbriata and G. coiyli are found on 



hornbeam and hazel respectively. 



Gnomonia Cesati & de Notaris (p. 264) 



Perithecia covered, or eriunpent, submembranous, glabrous, 

 ostiole more or less elongate; asci elUpsoid or fusoid, apically thick- 

 ened, opening by a pore; spores elongate, hyaline, 2 to 4-celled; 

 paraphyses none. 



There are some sixty species. Fusicoccum, Myxosporium, Sporo- 

 nema, Glceosporium, Marssonia, Asteroma, Leptothyrium occur in 

 some species as the conidial form. The ascigerous form usually 

 follows as a saprophyte after the parasitic conidial stage. 



G. veneta (Sacc. & Speg.) Kleb.^^'- ^^^- ^^^' »35 



Perithecia immersed, subglobose or sUghtly flattened, 150- 

 200 n, short, rostrate; asci long-clavate, 48-60 x 12-15 n, gen- 

 erally bent at right angles at the base, apically very thick, opening 

 by a pore; spores 14-19 x 4-5, straight 

 or slightly curved, unequally 2-celled, 

 the upper cell longer. 



Conidia variable in habitat, and 

 habit. (1) ( = Glceosporium nervise- 

 quum) acervuli subcuticular 100- 

 300 n; conidiophores short, conidia 

 oozing out in a creamy-white mass, 

 hyaline, ellipsoid, 10-14 x 4^6 ju, 

 pointed at one end and rounded at the 

 other. (2) ( =G. platani) acervuli sub- 

 epidermal, conidiophores long; conidia 

 as above. (3) ( =Discula platani=Myxosporium valsoideum) form- 

 ing minute, subepidermal, erumpent pustules on twigs; conidia 

 elliptic to oblong, hyaline, 8-14 x 4-6 m; (4) ( =Sporonema platani 



Fig. 204.— G. veneta, perithe- 

 cium. After Edgerton. 



