INJURIES INDUCED BY PLANTS 71 



ruptured, and the grapes in consequence begin to decay. So far 

 only the gonidia have been discovered, and it remains to be 

 determined how the fungus survives the winter. 



THE TRUFFLES, TUBERACEJE 



The Truffles are distinguished by having round subterranean 

 closed fructifications (cleistocarps), in which the asci are produced 

 on hymenia which clothe the surfaces of contorted passages. 

 Gonidia and sexual organs are unknown. 



Through the investigations of Rees 1 it was first established 

 that the stag truffle, Elaphomyces granulatus^ develops its 

 mycelium parasitically on the roots of pines. It is further 

 known that the edible species of truffle of the genus Tuber are 

 parasitic on the roots of the oak and beech. Frank has re- 

 cently devoted much study to the occurrence of fungal growths 

 on the roots of phanerogamic plants, especially Coniferce and 

 Cupuliferce, and has proved that mycelial growths are widely 

 distributed on the tender apices of the roots of trees. The outer 

 surface of young roots may be so closely covered by the 

 mycelium, which penetrates into and between the cells, as to 

 form a dense fungal mantle. Owing to luxuriant branching 

 and growth of the tissues the infested roots to some extent 

 display abnormal forms, while a sort of symbiotic condition 

 arises similar to what we find associated with many other plant- 

 parasites. When the cortical tissue of the roots has been 

 infested by the fungus for some time, it dies, and should the 

 fungal filaments penetrate into the internal tissues the roots 

 themselves die off entirely. Frank has designated these 

 phenomena by the name Mycorhiza, or fungus-root. It has not 

 yet been determined how many species of fungi take part in 

 these phenomena, and, especially, whether fungi belonging to 

 other groups besides the Tuberacece form MycorJiiza. Frank 

 holds the view that these root-fungi, by assisting in nutrition 

 and by conveying organic plant-food from the soil, play an 

 important part in the life of trees.* 



1 Dr. M. Rees and Dr. K. Fisch, Untersuchtmgen iiber Bau und Leben 

 der Hirschtrufiel, "Elaphomyces? 1888. 



* [The best account of Frank's views for the student is in his Lehrbtich der 

 Botanik, B.I. 1893. ED.] 



