62 RESEARCHES ON FUNGI 



by the perithecia was about 2,500 square mm., the number of 

 separate perithecia must have been about 20,000. Each active 

 perithecium was discharging eight ascospores from a single ascus 

 at short intervals of time, and thus, collectively, the perithecia 

 were liberating enough spores to form the thin spore-cloud visible 

 to the naked eye. It was observed that each ascus jet, like that 

 of a Peziza, 1 broke up immediately after being shot outwards, so 

 that the eight spores separated from one another and came to float 

 separately in the air (Fig. 19, A). An examination of a spore- 

 deposit showed that the spores were lying apart from one another 

 and therefore had fallen as individuals and not in heaps of eight. 



The number of spores produced by the parasite is consider- 

 able, as the following calculation will show. A fruit-body with 

 a diameter of about 4 inches gives rise to about 20,000 peri- 

 thecia, and each perithecium contains several hundred asci. Let 

 us assume that, on the average, there are 400 asci in each peri- 

 thecium. There are 8 spores in each ascus. The total number 

 of ascospores produced on the under side of the parasitised fruit- 

 body will therefore be about 20,000 X 400 X 8 or 64,000,000. 

 It is clear, therefore, that every parasitised fruit-body liberates 

 many millions of spores and that the largest fruit-bodies, i.e. those 

 which are 4-5 inches in diameter, liberate upwards of 50,000,000. 

 The discharge of the ascospores from the mouths of the numerous 

 perithecia of a single parasitised Lactarius continues for several 

 days. Some fresh fruit-bodies in which spore-discharge was 

 apparently just beginning were collected in a wood and set up- 

 right in a large glass damp-chamber in the laboratory. Some 

 black paper was then placed underneath the pilei ; and the paper 

 was changed daily. During the first four or five days a thick 

 white spore-deposit collected on the paper ; but, after this, the 

 daily deposit grew thinner until it ceased to be produced. I came 

 to the conclusion that, under favourable conditions, the length 

 of the spore-discharge period of the parasite on a single Lactarius 

 is normally from one week to ten days, i.e. about the same length 

 as the spore-discharge period of many Agaricaceas 2 and, not 

 improbably, of an unparasitised Lactarius piperatus. 



1 Of. vol. i, 1909, pp. 234-236. 2 C'f. vol. i, 1909, pp. 102-104. 



