RELATIONS OF SAPROPHYTES TO THEIR NUTRIENT SUBSTRATUM. 117 



part microscopic, all of which cannot be classed as saprophytes, but which, in order 

 to be able to thrive in the tracks of trickling water, must have the capacity of 

 surviving desiccation for weeks, and even months, on the barren rock after having 

 been previously supplied with copious moisture for a time. In the case of lichen- 

 growths in particular these are very favourite sites; and when the lichens cover 

 a large area they attract one's attention from afar. In limestone ranges, the 

 light-gray rock of steep declivities, interrupted by ledges covered with grass and 

 low brushwood, is extensively coloured by dark vertical bands and streaks, and the 

 effect is the same as if a dye had flowed from the ledges over the face of the rock. 

 These dark streaks indicate the course of the water which oozes from the humus 

 and renders possible the existence of numberless minute plants on the precipitous 

 face, in particular several dark crustaceous lichens {Acaros2^ora glaucocarpa, 

 Aspicilia fiavida, Lecidea fuscoruhens, Opegrapha lithyrga, &c.). 



The quantity of organic compounds brought down in solution by the water 

 which filters from the layers of humus on rocky ledges, and that which trickles 

 down the bark of trees, is, however, very small. Still, it is amply sufficient to 

 meet the requirements of the plants occurring at the spots in question. The claims 

 made by them upon their nutrient source are very moderate. We may here recall 

 the instances previously mentioned of mycelia of fungi which have been found 

 satisfied with the scarcely perceptible quantities of organic compounds in water 

 filtering into the shaft of a mine, and in the pure water of a mountain spring 

 respectively. To these instances must here be added the production of mycelia 

 in the wooden pipes through which the clear water of mountain springs is con- 

 veyed. After these pipes, which are made from the trunks of pines, have been 

 used as conduits for years, and their inner layers of wood have long since been 

 washed out, the mycelium of the fungus Lenzites sepiaria is not infrequently 

 developed within them, and in such luxuriance, indeed, that it forms great j^ellowish- 

 gray flocculent masses, which issue from the pipe's inner surface, and float in the 

 stream of running water. In time these flocculent masses increase in the clear 

 spring-water to such a degree that the pipes become completely blocked, and the 

 flow of water is arrested. And yet the water conducted through the pipes is so 

 pure, where it enters into and issues from them, that the residue obtained by the 

 evaporation of hundreds of litres afforded no trace of any organic matter. 



Seeing that most saprophytes absorb only such a comparatively small amount 

 of organic matter, one is all the more surprised to notice that a large number of 

 them fall suddenly, at certain times, into the opposite extreme. People speak of 

 things rapidly produced in abundance as " mushroom-growths ", and as " shooting up 

 like fungi ". The fructifications of many fungi are in fact developed with a rapidity 

 which borders on the miraculous. The various species of Coprinus living on dung 

 produce their long-stalked, cap-shaped fructifications during the night, and by the 

 evening of the next day the caps have already fallen to pieces, and are in a state 

 of decomposition, and nothing is to be seen in their place but a black deliquescent 

 mass like a blot of ink. The weight of this fructification, thus matured within 



