530 THE PATHOGENIC SLIME-FUNGI. 



killed cells, and a lighter coloured peripheral part. The cells 

 of young tubercles contain multinuclear plasmodia, which at the 

 time of spore-formation break up into portions round each 

 nucleus (spore-mother cells). These portions then divide into 

 four spores, each with a nucleus. The spores remain enclosed 

 in a delicate membrane as spore-tetrads, the characteristic feature 

 of this species. The upper part of leaves containing galls 

 frequently died. 



Sorosphaera. 



Spores enclosed in large numbers in a delicate membrane, 

 and forming a single layer round a central cavity. 



Sorosphaera veronicae Sehroet.^ causes quill-like outgrowths 

 and malformations in the stems and leaf-petioles of species of 

 Veronica ( V. hederifolia, V. triphylla, V. chamaedrys). The galls 

 consist of enlarged parenchymatous cells containing numerous 

 spherical or elliptical light-brown balls about 15 or 22/x broad. 

 The balls are enclosed in very delicate membranes, and consist 

 of a single layer of spores surrounding a small cavity. The in- 

 dividual spores are elliptical or oblong in shape, about 8-9 /u 

 long and 4-4' 5 ^ broad. 



III. THE PATHOGENIC BACTERIA. 



SCHIZOMYCETES. 



Although the bacteria and allied forms included in this 

 group are the cause of many diseases of mankind and of 

 warm-blooded animals, yet very few diseases of plants are 

 ascribed to their agency. The true Fungi, on the other hand, 

 which we have seen to cause so many diseases amongst plants, 

 only very rarely appear as enemies of the higher animals. The 

 few cases in which bacteria have been stated to cause injury 

 to plants are all as yet incompletely investigated and uncertain 

 in two respects. Thus although a plant-disease undoubtedly 

 exists accompanied by the appearance of bacteria, these bacteria 

 may not be the cause of the disease ; nor need it follow 

 that the phenomena accompanying an attack by bacteria are 

 necessarily symptoms of disease. On this account we shall 



' Schroeter, Enyler-Prantl natilrlicli. Pflanzenfamilien. 



