122 Minnesota Plant Diseases. 



some on bones, some on bees' nests, while others seem to pre- 

 fer animal remains and meat extracts. They are not, however, 

 either conspicuous in number or in size. (Fig. 49.) 



Green and blue molds (Aspergillacea). The blue and green 

 molds are amongst the best known and most conspicuous of 

 fungi. They are the great destroyers of food stuffs and as such 

 are well-known to every housewife. The common green or 

 blue mold is an accessory spore stage. In this form thousands 

 of threads stand upright side by side, each branches very pro- 

 fusely in broom fashion and each branch terminates in a long 

 row of pinched-off spores which are of the characteristic green 

 color. Millions upon millions of these spores may be produced 

 by a small patch of mold. Such mold spores are present in 

 great quantities in the air at almost any time of the year, so 

 that just as soon as any food-stuff is exposed to the air it may 

 be sown with green mold spores. These will quickly germi- 

 nate and will produce in a very short time often in a few days 

 another crop of mold spores. The green-mold spores, 

 though the most common, are not the only spores produced by 

 these fungi. There is also a sac-spore, though in most forms 

 it does not occur frequently in fact it is usually rare. These 

 sacs are spherical as in the loose-wefted fungi, but are found on 

 threads tightly woven together, and the whole spore-sac 

 mass is surrounded by a membrane-like wall or covering, which 

 is formed by closely united threads. These sac-capsules are 

 often yellowish or black and are seldom larger or even as large 

 as a pin-point. They are usually tiny spheres and of a solid 

 structure. The spores, when ripe, are released by the de- 

 cay of the capsules. There is no definite arrangement of the 

 sacs in the capsule nor is there a special opening through the 

 capsular membrane to allow of the escape of the spores. In 

 some forms, at least, a breeding act precedes the formation of 

 the capsule. The green and blue molds are especially fond of 

 bread and other starchy materials, preserves, etc. They are 

 also found on cheese and some varieties of mold are used to 

 ripen the cheese, where the flavor is largely due to the green 

 mold present. They are frequently found in preserved fruits 

 and jells and also as simple parasites, causing mold-rots of 

 fruits. (Figs, i, 1 88, 189.) 



