212 CALIFORNIA ACADEMY OF SCIENCES. [Proc. jn Skr 



Petri dish could not settle on the surface intended for the 

 culture. The sterilized cover-glasses, although carefully 

 kept "butter-side down," might readily become infected 

 by air-currents set up by the necessary movement of the 

 cover-glass and by lowering the cover of the Petri dish. 

 Apart from such accidental infection, the possibility of 

 which was carefully reduced to the minimum, the only 

 bacteria which could get into the cultures were those car- 

 ried in with the spores. The considerable force with which 

 the spores are discharged is indicated, as others have 

 repeatedly shown, by the distance to which they go. This 

 force is developed by the swelling, when wet, of the gelat- 

 inous walls of the paraphyses and other cells forming the 

 contents and the walls of the apothecia. In less than five 

 hours, enough spores will usually be ejaculated upon the 

 cover-glass to justify sealing it over a concave slide. 



Spores collected thus upon cover-glasses spread thin with 

 agar-agar or gelatine germinated in seven Ways. At the 

 same time I collected spores upon cover-glasses introduced 

 dry into the Petri dish. Owing to the cooling of the labo- 

 ratory (from morning, when I set cover-glasses to collect 

 spores, to afternoon, when I sealed the cover-glasses on the 

 concave slides) there accumulated on the cover-glasses not 

 only the moisture carried by the spores, but also that con- 

 densed from the damp air in the dish. Thus a supply of 

 water at least adequate for germination was insured, what- 

 ever may be said of the nutrient value of such water. After 

 the same lapse of time (seven days) spores had germinated 

 on these cover-glasses. 



In all the cultures the number of spores germinated was 

 very small in proportion to the number sown. If I had 

 sufficient confidence in the suitableness of agar-agar and 

 gelatine for lichen cultures, and in the nutritive value of the 

 condensed and spore-carried water, I might draw a definite 

 and significant conclusion regarding the value of the spores 

 of R. reticulata as reproductive bodies. I do not feel jus- 

 tified in doing this, though I will call attention to two things. 

 First, there must be a very considerable number of spores 



