THE FUNGI WHICH CAUSE PLANT DISEASE 



139 



FiQ. 93.— S. fuckeli- 

 ana, attachment 

 organ. After Ist- 

 vanffi. 



On the apple the fungus shows two different modes of develop- 

 ment. In some cases the mycelium accumulates under the epider- 

 mis without producing spores, becomes dark colored and also 

 causes a darkening of the contents of the host cells, which results 

 in a black spot giving rise to the name black 

 rot. In other cases ^^ the mycelium produces a 

 brown rot and abundant conidial tufts, ar- 

 ranged in concentric circles around the point 

 of infection. 



The form on pomaceous fruits has long been 

 regarded as identical with that on stone fruits; 

 but recently, at least in Eiu-ope, they have been 

 distinguished on cultural and morphological 

 grounds ' (see also ^ '"), as separate species, 

 the most distinctive character perhaps being 

 the color of the mass of conidia. In a similar 

 way S. laxa Ad & Buhl, is set aside as a distinct species infecting 

 only apricots. ^^^ 



American mycologists are inclined to doubt the distinctness of 

 the species on drupes and pomes in this country. 

 S. fructigena (Pers.) Schr. 

 Apothecia from sclerotia produced either 

 in or on mummied fruits, 0.5-3 cm. high, 

 stem dark brown, disk lighter, 5-8 or even 

 15 mm. in diameter; asci 125-215 x 7-10 /*; 

 spores ellipsoidal, 10-15 x 5-8 (i. 



Conidia ( =Monilia fructigena Pers.). Co- 

 nidiophores covering the fruits of the host 

 with a dense mold-like growth of light 

 brownish-yellow or ochraceous color; spores 

 averaging 20.9 x 12.1 /i. On stone and 

 pome fruits, especially the latter. 

 S. cinerea (Bon.) Wor. 

 Apothecia and asci similar to those of 

 S. fructigena, Conidia (=Monilia cinerea 

 Bon.). Conidiophores covering the fruits 

 with a dense grayish mold-like growth; spores averaging 12.1 x 

 8.8 It. On stone and pome fruits, especially the former. 



Fig. 94. — Typical conid- 

 iophore and conidia 

 of the Botrytis-form 

 of S. fuckeliana. Af- 

 ter Smith. 



