70 



BOTANY. 



conidia, which shrivel up. A careful examination reveals the presence of 

 very fine filaments within those of the mildew, which may be traced up to 

 the base of the conidial branch, where the receptacle of the parasite is 

 forming. The spores contained in these receptacles are very small (Fig. 

 39, K), and when ripe exude hi long, worm- shaped masses, if the recep- 

 tacle is placed in water. 



The mildews may be divided 

 into two genera: Podosphcera, 

 with a single ascus in the spore 

 fruit; and Erysiplie, with two 

 or more. In the latter the 

 archicarp branches, each branch 

 bearing a spore sac (Fig. 41, B) . 



The appendages growing out 

 from the wall of the spore fruit 

 are often very beautiful in 

 form, and the two genera given 

 above are often subdivided ac- 

 cording to the form of these 

 appendages. 



A common mould closely 

 allied to the mildews is found 

 on various articles of food when 

 allowed to remain damp, and is 

 also very common on botani- 

 cal specimens that have been 

 poorly dried, and hence is often 

 called " herbarium mould " (Eu- 

 rotium herbariorum) . 



FIG. 42. A, spore bearing filament 

 of the herbarium mould (Euro- 

 tium), x 150. B, C, another species 

 showing the way in which the 

 spores are borne optical section 

 x 150. D, spore fruit of the 

 herbarium mould, x 150. E, spore 

 sac. F, spores, x 300. G, spore- 

 bearing filament of the common 

 blue mould (PenicilUum), x 300. 

 sp. the spores. 



The conidia are of a greenish color, and produced on the ends of upright 

 branches which are enlarged at the end, and from which grow out little 

 prominences, which give rise to the conidia in the same way as we have 

 seen in the mildews (Fig. 42, A). 



Spore fruits much like those of the mildews are formed later, and are 

 visible to the naked eye as little yellow grains (Fig. 42, D}. These con- 

 tain numerous very small spore sacs (E), each with eight spores. 



