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, Cratmgus pyracantha. In consequence of this 

 variety in its habitat it is not surprising that it has received a variety 

 of names. Spiloccea Ponii, Fr., Helminthosporium Pyrorum, Desm., 

 Cladosporium Pyrorum, Berk., Cladosporium dendriticum, Wallr., 

 Gladosporium orbiculatum, Desm., Actinonema Cratcegi, P. & A., 

 Actitionema Pomi, Lev., and Phlyctidium Cratcegi, Wallr., are some of 

 the synonyms that have been at one time or another applied to the 

 forms of this fungus. 



Penicillium glaucum, Grev. Orustaceous Mold. (Plate 4, figs. 4- 

 10.) Soft decaying spots, of a peculiar brown color, somewhat re- 

 sembling that of dead leaves, 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. 

 Each 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 the 

 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 



