Minnesota Plant Diseases. 



197 



usually enclosed in cases which have definite methods of open- 

 ing. The spore mass is dusty or smut-like and the spores are 

 tiny spheres of microscopic size. If the spores be placed under 



favorable conditions of moisture 

 and temperature they do not 

 send out a fungus thread as do 

 true fungus spores, but the wall 

 breaks and the protoplasmic con- 

 tents emerge in a naked mass, 

 not unlike a very tiny drop of al- 

 bumen in appearance. This 

 small mass creeps about by 

 changing form, engulfs food, and 

 lives in all essentials as do other 

 very simple animals. After a 

 time a large number of these ani- 

 mals of the same kind meet and 

 soon fuse together forming a 

 larger mass of jelly-like material 

 which is known as a plasmodium. 

 The Plasmodium is often met 

 with on the forest floor or in 

 other moist places and is often 

 highly colored. Pink and yellow 

 are common colors though many 

 are yellowish white. The Plas- 

 modium may be cake-like or may 

 be drawn out in various ways, as 

 into strands. It is in reality a 

 colony of slime-mold animals, 

 and this colony may move and 

 feed and otherwise behave as a 

 simple animal. After a time and 

 particularly as the atmosphere 

 becomes dryer the plasmodium 

 draws itself up into some kind of 

 a fruiting body which is often 

 composed of stalk and capsule. In the latter are found the spores 

 and also sterile threads, in appearance not unlike those found in 



Fig. 100. — A slime mold. 1. An opened 

 (on right), and an unopened fruiting 

 body. From the opened fruiting body 

 is seen a protruding fluffy mass of 

 threads (capillitium), which encloses 

 the spores as in a mass of cotton. 2. 

 An isolated thread of the capillitium 

 and a spore (highly magnified), (Ar- 

 cyria serpata)." 3. a, young snore 

 (Chondrioderma difforme) ; b the 

 same, germinating; contents are 

 emerging as a naked bit of pro- 

 toplasm; c same in the free swim- 

 ming stage; has a single swimming 

 lash; d same in amoeba stage; e sev- 

 eral amoeba-like masses fusing to 

 form a small Plasmodium; f a young 

 Plasmodium. 2 and 3 highly magni- 

 fied. 1 and 2 after DeBary; 3 after 

 Cienkowski. 



