423 



that flourish best when supplied with a medium amount of water are 

 called mesophytes. 



We are apt to think of all fungi as requiring a great deal of water 

 for their best development. That is true of a large number of fungi 

 but by no means of all. The great majority of mushrooms are meso- 

 phytes, while others, especially some of the shelving forms that grow 

 on wood, are pronounced xerophytes. Practically all of these require 

 an abundance of water for the development of their fruit bodies but 

 they do not flourish in a soil that is continuously saturated with water. 

 For this reason one often finds that in a wood of which part is very 

 low land and part higher land many more kinds of mushrooms are 

 found on the higher land than on the low land. Nevertheless in the 

 case of most mushrooms no fruit bodies are developed except during 

 rainy weather so that a wet season is always a good mushroom season. 

 Although some of the smaller mushrooms do literally "spring up over 

 night", the most of those that are large enough to be worth collecting 

 for the table require at least two or three days for their development. 

 During a dry season, therefore, a single rain is not likely to bring us 

 a' good crop of mushrooms. It must be followed within one or two 

 days by a second or third in order to complete the development of 

 those fruit bodies that w^re started by the first shower, and the very 

 best time for mushrooms is when it rains a little every day or two. 



Parasites and Saprophytes. — Plants which are green, or have green 

 parts, such as grasses, trees, etc., make little if any use of ready-formed 

 foods. They manufacture their own foods from the carbon dioxide 

 of the air, water, and mineral salts obtained from the soil. But plants 

 which have no "leaf green", as the fungi, cannot do this. Such plants 

 may live upon, and get their food from, other living plants or animals, 

 in which case they are called parasites, or they may live on the dead 

 remains of plants and animals, and are then called saprophytes. 



A considerable number of our mushrooms are quite destructive 

 parasites. The heart-rots of forest trees are in most cases due to the 

 growth of the mycelium of certain shelving mushrooms. There are 

 also a few kinds, such as Ar miliaria luellea (page 489), which are 

 parasitic on the roots of trees, and sometimes kill the trees which 

 they attack. Many of the umbrella type of mushroom, as well as some 

 puffballs, are more or less harmless parasites on the roots of trees and 

 other plants, causing the production of structures known as mycor- 

 rhizas. These will be discussed presently. There are also a number 

 of mushrooms that are parasitic on other mushrooms. The common- 

 est of these, perhaps, is Stropharia epiuiyces (page 495), which is a 

 parasite on the shaggy-mane (page 479) and the inky-cap (page 481) 

 mushrooms. This plant never grows independently on the ground 



