34 Thirty-fourth Annual Report of the 



that compose them are so closely united that it is not possible to dis- 

 tinguish them easily. They appear to form a single white stem crowned 

 with a mass of spores. This form of the fungus is represented in fig. 

 7. It was at one time thought to be, not merely a distinct species, but 

 a distinct genus, and was named Coremium lencopus (the white 

 stemmed Coremium) by Persoon. It was also called Floccaria glauca 

 by the celebrated Greville. It is now regarded simply as a variety of the 

 crustaceous mold and takes the name variety Coremium. Sometimes 

 the fertile threads go to the other extreme and become excessively loose 

 and elongated in their mode of growth and send off a few fertile 

 branches as represented in fig. 8'. 



Although so commonly found on decaying apples, this fungus is not 

 limited to that habitat. It occurs also on pears and other fruits and 

 various decaying vegetable substances. 



Besides the synonyms already given, Byssus scoparia, Fl. Dan., and 

 Penicillium crustaceum, Fr., may be mentioned. 



Oidium fructigenum, Knz. and Schm. Fruit Oidium. (Plate 4, 

 figs. Ii-15.) Small, mealy-looking cushions or pustules sometimes oc- 

 cur on the surface of apples. Single ones are scarcely larger than the 

 head of an ordinary pin, but sometimes two or more occur so near 

 each other that they appear to run together and form larger and ir- 

 regular masses. Their color is not very decided, but it is generally a 

 dingy-white or grayish-yellow or a brownish-yellow, with a slight tinge 

 of red. When very old they sometimes assume a blackish tint. They 

 break out over a part or even over the whole surface of the apple, and 

 are said to be more abundant in dry than in wet seasons. The exter- 

 nal visible part of the fungus consists of short more or less densely tufted' 

 threads, each one surmounted by a string of spores. These are some- 

 what elliptical or egg-shaped, from which feature the generic name ap- 

 pears to have been derived. As in most species whose spores are produced 

 in necklace-shaped strings the spores readily separate from each other. 

 In this fungus they are much larger than in the crustaceous mold al- 

 ready noticed. The fungus attacks also pears, peaches, plums, etc., 

 and is therefore appropriately called the " fruit Oidium." With us it 

 is especially common on plums. It does not always wait for the fruit 

 to fall from the tree, but often attacks it while yet attached to the 

 branches. Dried and withered plums yet dotted with the fungus cush- 

 ions may sometimes be found still hanging on the trees in the spring 

 of the year. It is even claimed by one writer that fruit is preserved 

 by this fungus rather than destroyed. But my observations indicate 

 that it does not preserve in an uninjured and pure condition. It first 

 produces a kind of rot in the fruit, a "dry rot" perhaps it may be 

 called. It is perhaps less pulpy and soft than the rot produced by some 

 fungi, but the flesh becomes discolored and changed under the influ- 

 ence of the mycelium. Some experiments illustrative of this were made 

 by the writer with peaches. 



On September 25th spores of the fungus were planted on a sound 

 peach in three places ; on the rind, on the scar that marks its place of. 

 attachment to the branch, and on the flesh which had been exposed by 

 cutting away a minute portion of the rind. Those planted on the scar 

 were at the same time moistened by a drop of water. 



On the next day there was a slight discoloration about the scar. A 



