1911] The Ottawa Naturalist 133 



Spores produced in pycnidia or peritheeia may either ooze out, 

 or be expelled with force through a hole at the apex of \ he 

 fruiting bodies. Others again are freed by the collapse or decay 

 of the conceptacles in which they are produced. When ripe the 

 spores either pass through a period of rest, as winter spores, 

 or they immediately germinate, when they mav be regarded 

 as summer spores. Germination can only be accomplished 

 successfully when there is sufficient moisture available. Hence 

 we all have had the experience of seeing some fungus disease 

 spreading rapidly during moist warm weather (Apple and Pear 

 Scab, Potato Disease, Mildews, and others). Under favourable 

 conditions the spores take up a large quantity of water and begin 

 to swell, often to double their original size. The next step in 

 germination is a rupture in a cell wall and the protruding of a 

 germinal hypha, which is pushed into the particular substratum 

 (leaf, twig, etc.), where it quickly begins to ramify. We have 

 considered previously the great variation of the fungus spores. 

 The germination of the various spores is likewise very different 

 and frequently an important factor for distinction of species. 

 Conidiospores most generally germinate by producing directly 

 one or more germinal tubes which are capable of infecting plant 

 tissues. Smut spores, however, produce first a so-called short 

 promycelium on which secondary and even tertiary spores may 

 be formed which on germination produce the tube causing 

 infection. The loose smuts of barley and wheat, however, 

 produce infection tubes directly. Similar in behaviour are the 

 teleutospores of our rust fungi. They also produce a promy- 

 celium and secondary spores when germinating. 



Still more different is the germination of the spores of the 

 common potato fungus. Here the contents of the conidia pro- 

 duced by segmentation of the branches breaks up into minute 

 microscopic bodies, which for some time may be seen rapidly 

 swarming about. After a very short period, however, these 

 swarm spores become stationary and their walls thicken until 

 they finally germinate by producing the typical infection tube. 



There are numerous fungi which produce both summer and 

 winter spores. The Black Knot of plums and cherries, the 

 Powdery Mildew of grapes, Scab of pears and apples all produce 

 two forms of spores. The ascospores are nearly always winter 

 spores. The teleutospores of rusts, or egg spores of the Peron- 

 osporae, which cause the downy mildews are not ascospores, 

 though typical winter spores. The summer spores serve the 

 purpose of a rapid propagation of the fungus, while the winter 

 spores are responsible for carrying diseases over the winter. 

 Very rarely may summer spores be carried through the winter 

 alive, owing to their feeble protection and short life. The winter 



