84 Journal of the Mitchell Society [Septfinhcr 



the Melanconiceae and is accordingly transferred to this family of 

 imperfect fungi. 



Vicia sativa and V. villosa become severely affected under condi- 

 tions in which V. angustifolia aiid V. flasijcarpa remain practically 

 free from disease. 



West Raleigh, N. C. 



Explanation op Figures 

 PLATE 2 



Figs 1-7 and 9-11 inclusive, are drawn to the same scale. 



Fig. 1. Copy of unpublished camera lueida drawings of Proiocoronospora nigri- 

 cans, made by Dr. C. W. Edgerton in 1907. The conidiophores show several 

 stages of conidial formation in whorls at the apex. The formation of 

 yeast-like buds upon germination of conidia is also illustrated. 



FiG". 2. Normal conidia of Protocoronospora nigricans taken from diseased 

 vetch. 



Fig. ;■). Germination of conidia in hanging drops of tap Avater in which vetch 

 stems have been macerated. Septation and the formation of one or more 

 germ tubes is shown. 



Fig. 4. The usual type of germination by budding as occurs in tap water, 

 plain agar or various kinds of nutrient agar, 24 to 48 hours old. 



Fig. 5. A type of germination not uncommon on a variety of nutrient agar. 



Fi<i. 6. In agar cultures in which certain conidia germinate as in Figs. 4 and 

 5, others form a thickened, short mycelium which si^orulates terminally or 

 from lateral branches. 



Fig. 7. Abnormal conidia as appear in old cultures on corn meal. 



Fig. 8. Vertical section through a lesion on young vetch pod. 



(a) Conidia, conidiophores and fungous stroma; 



(b) Hypodermal parenchyma occupied by intracellular mycelium; 



(c) tSclerenchyma tissue of pod wall; 



(d) Embryonic cells of the younger seed. The palisade-like cells be- 

 come the Malphigan layer in the mature seed. 



Fig. 9. Characteristic short mycelium in agar cultures four days old, showing 

 abundant conidial formation. 



Fig. 10. Much branched mycelium Avith few or no conidia found in the same 

 cultures as the condition represented in Figs. 6 and 9. 



Fig. 11. Sterile mycelium from four day old nutrient agar plates. 



Fig. 12. Section of mature infected vetch seed, showing the mycelium of Pro- 

 tocoronospora in the various tissues; 



(a) Malphigian layer, the outer wall of wliose cells is very much 

 thickened and shows the characteristic ' ' light line ' ' so common in 

 seeds of eguminoseae; 



(b) Scleroid layer; 



(c) Vestigal nucellar tissue; 



(d) Epidermis of the cotyledon; 



(e) Cotyledonary tissue abundantly filled with starch. 



