VARIOUS OBSERVATIONS 67 



resistance of the air. There is no doubt that the trajectory of each 

 one of these ascospores is a sporabola and in general form resembles 

 that of Psalliota campestris and of Amanitopsis vaginata of which 

 illustrations are given in Volume I. 1 



The ascus-apparatus for discharging projectiles is not so delicate 

 as the basidial. From a sterigma of a basidium the spore is usually 

 shot only about 0-1-0-2 mm., but from a normal ascus, where 

 the eight spores must be squirted out in a jet together, the distance 

 of discharge is in general not less than 0-5 cm., often 1-3 cm. 

 (Pezizae, etc.), and sometimes as much as 35 cm. (Ascobolus 

 immersus). 2 We may regard the normal ascus, therefore, as an 

 apparatus which, by the very nature of its construction, while 

 unfitted for propelling its spores so small a distance as 0-1- 

 0-2 mm., is admirably fitted for shooting them to a distance of 

 the order of 1 cm. Now this fact is correlated, so it seems to me, 

 not only with the entire absence of narrow hymenial tubes, closely 

 packed gills, closely packed spines, etc., in the fruit-bodies of the 

 fleshy Ascomycetes, but also with the suppression of the gills in 

 our parasitised Lactarius piperatus. Let us suppose for a moment 

 that in the parasitised fruit-body of this species the gills were not 

 suppressed but were crowded together in the normal manner, 

 with interlamellar spaces varying from about 0-5 mm. to 1-2 mm. 

 in width ; and let us further suppose that the perithecial stroma 

 completely covered these gills, so that the mouths of the peri- 

 thecia looked horizontally into the interlamellar spaces. Then, 

 the mouths of the perithecia would be so near to the opposing 

 gills that the asci would shoot their spores right across the inter- 

 lamellar spaces, and the spores, owing to their adhesiveness, would 

 stick to the gills which they struck. The consequence of this 

 would be that very few of the discharged ascospores would ever 

 fall into the interlamellar spaces and thus escape from the fruit- 

 body, and the dissemination of the spores of the parasite by the 

 wind would be rendered practically impossible. From these 

 considerations we see that the suppression of the gills of the para- 

 sitised Lactarius is a condition of the greatest importance to the 

 welfare of the parasite, and that this suppression is therefore fraught 

 1 Vol. i, 1909, p. 185. 2 Ibid., p. 252. 



