PHYTOPHTHORA. 



119 



Another parasite of conifer seedlings — Fusoma parasitictmi — 

 which somewhat resembles Phytophtlwra, is figured and described 

 amongst the " Fungi imperfecti." 



Phytophthora infestans, De Bary.^ This parasite was first 

 observed in Europe in 1845, and has since then become 



Fig. so. 



Fig. 29.— Celhilav tissue from diseased cotyledon of Beech. The starch-grains 

 have been absorbed from the cell-protoplasm which has shrunk away from the 

 cell-wall a ; b, h, intercellular fungal hyphae with very tiny haustoria ; c, c, 

 fertilized oogonia, each containing a single oospore. (After R. Hartig.) 



Fig. ZQ.— Phytophthora omniviyra on the epidennis of a Beech-cotyledon, p., 

 Outer wall of epidermal cell ; h, cuticle ; c, hyphae growing between cell-wall 

 and cuticle, causing the slight protuberance d\ e, spot where a hypha has 

 emerged through the cuticle and developed as a sporangiophore/; after the first 

 sporangium has reached matunty a second begins to form, g and h, whereby the 

 first is displaced ; h, a stoma from which sporangiophores have developed. 

 (After R. Hartig.) 



only too well known. It attacks leaves, shoots, and tubers 

 of potato and other Solanaceae, e.g. the tomato {S. Ly coper dcum). 

 The potato leaves become discoloured, brown-spotted, and 

 crumpled, especially in damp weather. The sporangiophores 

 (gonidiophores of De Bary) issue from the stomata in 



1 De Bary, Journal of Botany, 1876, and Journal of the Royal Agric. Society, 

 1876. 



