EXPLANATION OF PLATES. 



[All ^gures are magnified 540 diameters, except where otherwise specified.'] 



PLATE I. 



ScLEROTiuM Disease op Cucumber (ScUrotinia Libertiana F'k'l.). 

 Stems and young fruit attacked by the disease, showing mycelium of the fungus, chiefly 

 at the nodes of the stems, and some external sclerotia. o, an early stage, the stem still 

 green; 6, later, the internode shrinking, and a sclerotium near the upper node; c, a late 

 staue, the parenchyma largely destroyed, and the stem yellow; d and e, at about the same 

 stage as b; fr., a young fruit, showing mycelium and sclerotia. Natural size. From a 

 photograph of fresh specimens. 



PLATE II. 

 Sclerotium Disease of Cucumber {Sclerotinia Libertiana F'k'l.). 



Fig. !• An elongated sclerotium from the interior of a stem. Natural size. 



Pig. 2. An irreguhir sclerotium from the exterior of the host-plant. Natural size. 



Fig. 3. A sclerotium somewhat advanced in " germination," with two stalks. Natural 

 size. 



Fig. 4. Two views (a and b) of the same sclerotium, with fruit stalks, b four days older 

 than «. Natural size. 



Fig. 5. Two views of another " germinating" sclerotium, taken four days apart. Natu- 

 ral size. 



Fig. 6. A section from the interior of a mature sclerotium. X 350. 



Fig. 7. One of the fruit stalks shown in tig. 3, in vertical section. X 19. 



Fig. 8. Three asci and two paraphyses from a well-developed cup. One ascus with 

 forming spores, one with fully formed spores, and one after the escape of its 

 spores, sp. 



Fig- 9. Three ascospores germinated in water, after one day. 



Fig. 10. Three ascospores after one day in jarune infusion. 



Fig. 11. A well-developed young attachment organ. X 350. 



Fig. 12. A part of an old attachment organ. X 350. 



Fig. 13. Spore threads and conidi? {sp.) of Boirytis form, showing, y, young threads 

 before the formation of spores, and, o, old threads after the falling awaj' of 

 the spores. X 200. a, conidia more magnified. X 5-10. 



PLATE III. 

 Powdery Mildews. 

 Figs. 14-19. Of cucumber {Erysiphe Cichoracearum D. C). 

 Fig- 14. Epidermis of upper surface of leaf, with mycelium, m, of fungus giving rise to 



haustoria, h, and sjjore threads, sp. 

 Fig. 15. Three spore threads, with spores in various stages of development. 

 Fig- 16. Two ripe summer spores not yet fallen apart. 

 Fig. 17. Two ripe summer spores of a similar fungus from Ithaca, N. Y. 

 Fig. 18. A group of six spore sacs {asci), with spores, from the same perithecium. 

 Fig. 19. A ripe ascospore. 



FigB. 20-22. Of strawberry (Sphcerotheca Castagnei Lev. ?). 

 Fig. 20. A bit of mycelium, with a spore thread. X 200. 

 Fig- 21. The upper part of a spore thread, with developing spores. 

 Fig- 22. Two ripe summer spores. 



Figs. 23-24- Of gooseberry {Sphnerotheca .}fors-uv<f. (3z.) B. & C). 

 Fig. 23. The single spore sac produced in a perithecium, with spores. 

 Fig- 24. Four ripe ascospores. 



