INTRODUCTORY 3 



rotting bark, spreads between the cells, between the growth- 

 layers of the wood, runs in corded vein-like nets between the 

 wood and bark, and finds in all these cases nutrition in the 

 products of organic decomposition. Such a plasmodium may 

 be divided, and so long as suitable surroundings are main- 

 tained, each part will manifest all the properties of the whole. 

 Parts of the same plasmodium will even coalesce again. If a 

 piece of plasmodium-bearing wood be brought indoors, be 

 protected from desiccation by aid of a moist dark chamber, not 

 too warm (70 F.), the organism seems to suffer little if any 

 injury, but will continue for days or weeks to manifest all the 

 phenomena of living matter. Thus, under such circumstances, 

 the plasmodium will constantly change shape and position, can 

 be induced to spread over a plate of moist glass, and so be 

 transferred to the stage of a microscope, there to exhibit in the 

 richest and most interesting and abundant fashion the stream- 

 ing protoplasmic currents. As just indicated, the plasmodia 

 follow moisture, creep from one moist substance to another, 

 especially follow nutritive substrata. They seem also to 

 secure in some way exclusive possession. I have never seen 

 them interfered with by hyphas or enemies of any sort, nor do 

 they seem to interfere with one another. Plasmodia of two 

 common species, Hemiarcyria clavata and H. rubiformis, are 

 often side by side on the same substratum, but do not mix, and 

 their perfected fruits presently stand erect side by side, each 

 with its own characteristics, entirely unaffected by the presence 

 of the other. On the other hand, it is probable that some of 

 the forms which, judged by their different fructifications, and 

 by this alone, are to us distinct, may be more closely related 

 than we suspect, and puzzling phases which show the distinc- 

 tive marks supposed to characterize different species are no 

 doubt sometimes to be explained on the theory of plasmodial 

 crossing ; they are hybrids. 



Under certain conditions, low temperature, lack of moisture, 

 the plasmodium may pass into a resting phase, when it masses 

 itself in heaps and may become quite dry in lumps of consid- 



