May 22, 1916 



Hypoderma Deformans 



281 



periods of drying till on the fourth trial no spores were liberated. An 

 examination of the apothecia showed the asci to be entirely empty. 

 This experiment not only demonstrates that the fungus has the ability 

 to resist protracted periods of dryness but that the period of spore libera- 

 tion may be much protracted, depending upon the atmospheric humidity. 

 During wet weather apothecia expel their spores in visible quantity 

 when a sharp blow is given the branch bearing infected needles. 



Considering the long periods of drought in most yellow-pine regions, 

 it is safe to assume that an apothecium ripening in early spring may 

 first become emptied of its spores during the ensuing winter or even 

 later. This is important for the propagation of the fungus, since new 

 infections are possible from the time the first needles of the season appear 

 till the close of the growing season. 



In order to determine the viability of the spores expelled from apothecia 

 after long dryness, a 2 per cent sugar solution was introduced into the 

 cavity of one of the slides containing apothecia which 

 had lain dry in the laboratory for two months and 

 the slide placed in the thermostat at 35 C. On the 

 fourth day spores germinated readily. The germ 

 tubes appeared more frequently from the ends of the 

 spores. A slight addition of an extract of pine needles 

 to the sugar solution promoted germination. 



It was noticed that in collections of the fungus 

 made shortly after warm summer rains the asci are 

 frequently empty as compared with asci of mature 

 apothecia collected in the colder spring months. 

 This, it seems, may not be entirely due to a longer 

 period of spore liberation but also to the higher tem- 

 perature of the summer months. Von Tubeuf found 

 that increasing temperature promoted spore liberation 

 in Lophodermium pinastri and it is found to be true in experiments with 

 the yellow-pine fungus. During the winter, moistened apothecia from dry 

 material were mounted in two culture slides; one was placed outside the 

 laboratory during a period when the thermometer registered about 40 

 F. and the other was kept in the laboratory air of about 80 F. At 

 the end of four hours a microscopical examination showed that a large 

 number of spores had been ejected from the apothecia in the slide kept 

 in the laboratory but none from the other slide. When the slide from 

 the outside was allowed to stand for a while in the warm air of the 

 laboratory, spores were liberated in quantity. 



Although spores from various needle fungi are undoubtedly more 

 readily liberated during warm rains of the summer months, the frequent 

 drying of the foliage of the trees is probably not favorable for infection. 

 It is frequently observed, and as often reported, that needle fungi become 

 more active during the cool, protracted rainy periods of early spring and 

 late fall. No extensive data are at hand regarding the resistance of 



FIG. 4. The upper por- 

 tion of a young ascus of 

 Hypoderma deformans, 

 showing the formation 

 of the pore at the tip 

 through which the 

 spores are expelled. 



