State Museum oF NATURAL HISTORY. 33 
fungus with us occurs most frequently on apples, but its habitat is not 
limited to them. It sometimes appears also on apple leaves, and on 
pears and pear leaves and young twigs which it sometimes seriously 
injures. It has also been “found in “Europe, on thorns, particularly 
the evergreen thorn, Crategus pyracantha. In consequence of this 
variety in its habitat it is not surprising that it has received a variety 
of names. Spilocea Pomi, Fy. , Heiminthospori ium Pyrorum, Desm., 
Cladosporium Pyrorum, Berk., Cladosporium dendriticum, Wallr., 
Cladosporium orbiculatum, Desm., Actinonema Orategi, P.& A, 
Actinonema Pomi, Lev., and Phlyctidi um Crategi, Wallr., aresome of 
the synonyms that have been at one time or another applied to the 
forms of this fungus. 
Penicillium glaucum, Grev. Crustaceous Mold. (Plate 4, figs. 4- 
10.) Soft decaying spots, of a peculiar brown color, somewhat re- 
sembling that of dead leav es, often make their appearance on apples, 
especially if they are stored in a warm place. Frequently a species of 
mold develops on these spots. At first minute white tufts appear but 
they soon acquire a pale bluish-green color, which is indicated botani- 
cally by the word “glaucous.” ‘These tufts are usually about as large 
as the head of an ordinary pin. Generally they become so numerous 
and so closely crowded together that they form a continuous patch or 
crust, which would render the name “ crustaceous mold ” appropriate, 
although this name was probably suggested originally by the patches, 
sometimes formed by the sterile threads of the fungus, If the decayed 
portion of the apple be examined microscopically, numerous slender 
fungoid filaments will be found running through it in every direction. 
These are the mycelium of the fungus, the immediate cause of the rot. 
As the roots of-a tree absorb nourishment from the soil that surrounds 
them, so the threads of this fungus absorb their nourishment from the 
apple cells that surround them. ‘They spread more or less rapidly till 
the whole apple is rendered worthless. When they come to the surface 
or reach an air cavity, such as exists about the seeds, they send up 
fruiting stems if the conditions are favorable. These stems are deli- 
cate jointed threads which give out near the top one or more pairs of 
short opposite branches, which are themselves once or twice forked, 
Hach ultimate branchlet bears at its tip a string of spores, looking 
much like a string of minute beads. The branches are so short that 
they are scarcely visible unless highly magnified They with their 
- strings of spores resemble a minute inverted tassel. The strings of 
spores are so numerous that they give a dusty appearance to the fun- 
gus and often hide from view the threads that support them. Their 
attachment to the branchlets and to each other is very slight and easily 
broken. Even a drop of water spreading itself on the slide of the 
microscope will separate them if it comes in contact with them. A 
slight breath of wind is enough to scatter them far and wide. The 
separate spores are globular and range from twelve to twenty one- 
hundred thousandths of an inch in diameter. Five thousand of ee 
largest ones could be placed in a line in the space of one inch. 
As has already been intimated, the fertile threads often grow in 
clusters or tufts. Sometimes these tufts are so compact and the threads 
5 
