517 



appeared on the leaves, theu on the green branches, and finally on the 

 fruit. 



I determined to take advantage of its presence to make farther inves- 

 tigations in reference to its habits. I secured on a glass slide a few of 

 its oidium spores, placed them in a clean glass jar containing a little 

 water, excluded the atmosphere by a ground-glass stopper, and sub- 

 jected the jar to a temperature of about 75° Fahr. during the inves- 

 tigations. On the second day the spores were examined, when it was 

 found that many of them had germinated. 



1, group A, represents the oidium. I think that the spores in this 

 case are thrown out from the peduncle* in the same manner as soap- 

 bubbles from a pipe. I have never seen a case of an oidium spore hav- 

 ing a small spore attached to it as if in the act of reproducing a fac 

 simile of itself, as is so frequently observed in the spores of the common 

 yeast plant, {Torula cerevisia'.) The oidium spores germinated and 

 threw out branches as shown in the drawings 2, 3, and 4. The protrud- 

 ing branch of spore 2 differs in form from that of 3. The branched state 

 of 4 illustrates the changes which take place in 2. I have observed 

 many spores germinating like 3, upon the functions of which I have 

 been unable to decide. After exposure for a few days, more new forms 

 of fungi appeared on the branches of the mycelium of the oidium. (See 

 5 and its ramifications, group B.) Xos. 6 and 7 next appeared, followed 

 by 8 and 9 ; 10 represents a highly magnified spore of Penicillium 

 glaucum, 9 ; 11, the spores of 7 germinating, which resemble Penicillium 

 Armeniacum, Berk. The flask-shaped spores, 8, {Ajiteymar ia tenuis, Ness.,) 

 are generally the last to appear. They belong to a genus of Torulacei^ 

 remarkable for their close resemblance to a Florence tiask.t 



My object was to ascertain what changes, if any, would take place 

 during the germination of the spores. I therefore varied my experi- 

 ments in numerous ways, and am satisfied that the forms 6, 7, 8, and 9 have 

 no relation to the oidium under experiment, but are distinct fermenting 

 plants, living on and consuming the mycelium and spores of the 

 oidium, i^reventing the further healthy growth of the vine fungus. The 

 facts observed have an important bearing on the cultivation of foreign 

 grape-vines when grown in moist hot-houses, for since it has been shown 

 that parasitic fungi are nourished by the spores and mycelium of the 

 Oidium of the vine and grow profusely on them, the vine itself will be- 

 come affected by the growth of the fungi over its leaves, green branches, 

 and fruit. I have frequently transferred to varnished glass slides the 

 same class of spores direct from a leaf which had been kept unusually 

 moist while growing. These will doubtless hasten the death of the plant 

 on which they grow. The evidence is conclusive that when the flowers 

 of sulphur have been applied early to mildewed vines, they have been 

 saved, and that later applications have been unavailing. This may arise 

 from the fact that the other forms of fungi, such as I have pointed out, 

 may assist in the destructive work. These experiments have been re- 

 peated often under varied conditions, with an unvarying similarity of 

 results. A slip of glass was varnished, and, when nearly dry, a vine-leaf 

 covered with the Oidium was pressed on it, so that many of the spores 

 adhered to the varnish. When the slip was introduced into a moist 

 jar at the temperature mentioned, the spores adhering to the varnish 

 germinated, as shown at B. When placed in an atmosphere containing 

 turpentine, benzine, or carbolic acid, they failed to germinate, and the 



*The stem or stalk that supports the flower and fruit of a plaut. 

 t The microscopic dictionary says of this genus that " no British representatives of 

 this genus appear to have been recorded hitherto," (p. 29, vol. 1, second edition, 1860.) 



