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stopper. I examined it iu its different stages of growth, every twenty- 

 four hours, for several weeks. I have repeated these experiments many 

 times during the last six mouths, always getting the same general result. 

 The figure illustrates the various stages of growth. The fruit B repre- 

 sents the thousandth of an inch, and the scale A one y^^ of an inch. The 

 color of the fruit resembles that of matted silver, rich and somber. The 

 principal fruit-stalk, although represented as branched, is not always so 

 in nature. The stalk is frequently found supporting but one head or 

 fruit. The stalks, when fully ripe, are cellular and of a peculiar struc- 

 ture. 



In order to ascertain whether a rotting potato, which had decayed 

 from ordinary fungus fermentation, Penieillium glaucum, would produce, 

 under similar treatment, a fungus like Fig. 3, or one of a similar type, 

 I instituted a second set of experiments, using a mush made directly 

 from healthy potatoes. The experiments were conducted in tlie same 

 manner as those already described, extending over a period of six 

 mouths. The result was that the pulp of the healthy potato invariably 

 produced PenicilUum glaucum, while that of potatoes infested with 

 Peronospora infestans, with a like uniformity, produced the fungus 

 represented by Fig. 4. 



It Avould seem from experiments that the fungus Artoirogus liydno- 

 sporns is in some way peculiarly connected with Peronospora in/estans, or 

 '• potato rot ;" and during its highest stages of fermentation it would 

 also seem to have the power of destroying the germ of the fungus 

 PeniciUium glaucum. 



One of my early experiments with rotting potatoes consisted in placing 

 some of those affected with the fungus Peronospora infestans in a saturated 

 solution of sulphate of copper. After a lapse of four weeks I removed 

 the affected potatoes from the copper solution and placed them in pure 

 water, changing the latter every twenty-four hours, as long as the liquid 

 at the end of that time had the bluish tinge indicating the presence of 

 copper in solution. I next placed the potatoes in separate glass jars. 

 After the lapse of several weeks the water became slightly blue in color 

 still showing the presence of sulphate of copper. To my surprise the 

 mycelium of a fungus had grown in profusion on the potato, its branches 

 extending upward to the surface of the liquid. In the course of the 

 next two months little w^hite specks appeared on the surface. These 

 specks ultimately developed into distinct circular forms, resembling a 

 lady's low-crowned hat, having a thickness of about one-eighth of an 

 inch 'at the center of the crown, with a diameter of about half an inch, 

 and a pure snow-white color. All these disks finally united, covering^ 

 the surface of the liquid with a felt-like substance, which apparently 

 derived its sustenance from the potato, through the fungus branches 

 above referred to. On examining portions of this substance under a 

 jiower of three hundred diameters I found it to consist of white Peni- 

 eillium thickly matted together and in full fruitage. 



Sulphate of copper in solution has been frequently recommended as a 

 reliable antidote to fungoid growth. In the present experiments it evi- 

 dently destroyed the Peronospora infestans, but did not destroy the Peni- 

 eillium, the germs of which must have existed in the potato, as well as 

 those of the former fungus ; though it has already been seen that where 

 Peronospora infestans produced putrefaction the Penieillium never made 

 its appearance, its germs having probably been destroyed by the more 

 powerful fungus. It may be remarked, in conclusion, that the failure of 

 the solution of sulphate of copper to destroy Penieillium v^wdev^ it prob- 

 able that it would prove ineffective as an antidote to other forms of the 

 funji belonging to the family Muscedines. 

 3 A 



