Some Questions which they Suggest. 23 



conditions seem to cause them sometimes to retreat into 

 the wood to appear again under more favourable circum- 

 stances. Some plasmodia inhabit the interior of dead 

 wood, and only appear on the surface for the purpose of 

 fruiting : in the search for a suitable home for reproduction 

 it has been thought that they move away from damper to 

 drier spots, and they certainly often produce their sporangia 

 inthe dry air and in high positions. It has been thought also 

 that light has a tendency to make the plasmodia ascend 

 and darkness to descend. Sometimes a plasmodium will 

 ascend a tree or a post for a foot or more, and a species 

 known as Lycogala epidendron is said always to affect the 

 highest point of the substance on which it rests. It is 

 by no means infrequent for plasmodia to leave the dead 

 wood on which they have been living and to ascend the 

 stalks of flowering plants, or to spread over mosses, and 

 often we have been surprised at the distances travelled by 

 plasmodia in a few hours. The appearance, we may 

 remark in passing, presented by the sporangia of delicate 

 myxies on the leaves of mosses or blades of grass is 

 sometimes very beautiful. 



Plasmodia, as we have said, sometimes move in an 

 upward, sometimes in a downward direction ; in a seed, 

 as we know, these two tendencies are separated, and the 

 radicle tends to grow in the direction of gravity, and the 

 plumule against it ; in the myxies it would seem as if the 

 same protoplasm at one time had the one tendency, and at 

 another time the other. Perhaps, in passing, we may 

 observe that the fact that plants and trees for the most 



