236 PLANT LIFE. 



Under the microscope it is often like the finest lace- 

 work but the beautiful curves and orderly entanglement 

 of the threads are quite beyond description. These 

 threads are often ornamented with spiral lines or spines 

 which probably alter the expansion and contraction 

 when the amount of moisture changes. 



The spores are very often minutely spiny or warted, 

 and, in wet weather, will germinate in from 4 to 28 

 hours. Each spore becomes a small pear-shaped piece 

 of protoplasm, with a single whip or tail much longer 

 than itself The whip lashes, and coils itself round in a 

 very vigorous manner, and the spore is dragged about 

 in all directions, often turning somersaults. Thus, in a 

 wet film, on the wood surface, the spores are able to 

 explore every crack and crevice, until they find a spot 

 with suitable nourishment. They then fuse with one 

 another, and lose their whips or tails, becoming a slimy 

 mass of protoplasmic material, which is called the 

 Plasniodiuin. This seems to live and move like an 

 Amoeba. It can enclose bacteria or pieces of decaying 

 organic matter, and digest them. It can also move, 

 and it shows distinct preferences and objections as 

 regards water and chemical solutions. In colour these 

 Plasmodia differ ; they are white or rose-red, or some- 

 times yellow ; they are often very like the excrement 

 of birds. After a time they come to rest, and begin to 

 form the sack, spores, and capillitium. The spores are 

 formed round the nuclei of the plasmodium, and the 

 protoplasmic matter secretes the outside envelope and 

 the capillitium (see Lister, " Mycetozoa "). 



Some of these plasmodia are found on decaying 

 mosses or on dying grass leaves ; one species is very 

 abundant in old tanyards. A peculiar parasitic species, 

 Plasmodiophora Brassicae, is the cause of the " Finger and 



