7S6 FUNGI 



Many other substances, notably preparations of copper 

 (Bordeaux mixture, 'Fostite,' talc and finely-powdered copper 

 sulphate) have a more certain effect in destroying ' mould,' but 

 the application to hops is scarcely feasible on account of their 

 somewhat poisonous properties. 



Ex. 318. — Examine with a low power a mildew-spot on a hop-leaf. Observe 

 the chains of conidia. Pull off a piece of epidermis with the fungus on it. 

 Mount in water and examine with a high power. Draw the mycelium and 

 erect conidiophores. Observe the colourless vacuolated contents of the 

 hyphae and conidia. 



Ex. 319. — Cut transverse sections of a leaf through a mould-spot and 

 examine with a high power. Note the bladder-shaped haustoria in the 

 epidermal cells of the leaf. 



Ex. 320. — Examine the underside of mouldy hop-leaves with a lens. Speci- 

 mens are often most easily obtained from mouldy plants growing undisturbed 

 in hedges. Note the groups of small, round, dark-brown perithecia. Take 

 off some of the latter with fine forceps or needles and mount in water. 

 Examine with a low power and make drawings of the perithecia and their 

 filamentous appendages. 



Examine the same with a high power. Press firmly on the cover-slip with 

 the end of a lead pencil or other blunt piece of wood so as to rupture the 

 brown wall of the perithecium. Note the transparent single ascus and the 

 spores within it, also the thinner part of the apical wall of the ascus. 



Kose-mildew (^Spharotheca pannosa Wallr.) is a species very 

 common on cultivated roses. Its mycelium appears as a greyish- 

 white film on the leaves, young shoots, and flower-buds of the 

 plants, the parts attacked usually becoming more or less puckered 

 and otherwise deformed. 



The conidia and perithecia are similar in form and structure 

 to those of ^. Castagnei. 



The same fungus is met with on the peach and apricot. 



(ii) In the genus ErysipJie the conidia are similar to those of 

 Spharotheca, but the perithecia are somewhat flattened and con- 

 tain several asci instead of one only. 



Grass-mildew (Erysiphe graminis D. C.) is not unfrequently 

 responsible for considerable injury to cereal crops and grasses 



