GALLS CAUSED BY FUNGI 115 



Lady's Fingers. They contain bacteria-like organisms, and 

 are regarded by some authorities as examples of symbiosis 

 rather than true parasitism. 



The rootlets of trees belonging to the Cupuliferae are 

 often invested with hyphae known as Mycorrhiza. They 

 are usually seen in plants grown in soil where humus is 

 abundant, and would seem to be determined largely by the 

 rate of transpiration. Mycorrhiza are usually found in 

 plants with slow transpiration current, and some give rise 

 to definite gall-like structures on the roots and rootlets. 



The peculiar root tubercles on the Common Alder are 

 shown in Plate XVI., Fig. 4. They are not uncommon 

 on both large and small plants. They were first described 

 in 1829 by Meyen, who considered them " pseudomor- 

 phosed roots." At one time they were classed by Woronin 

 with the Mycetozoa under the name of Schinzia alni. Ac- 

 cording to the latest view, they result from the presence of 

 a hyphomycete, Frankiella alni (Wor.) Ren6 Maire. Hiltner 

 proved experimentally, in 1896, that these tubercles enabled 

 the plant to assimilate the free nitrogen of the air by a pro- 

 cess resembling that which occurs in leguminous plants, and 

 showed that Alder plants can grow without tubercles if 

 nitrogen is present in the soil, that the production of 

 tubercles is hindered if nitrogen is present in abundance, 

 and that calcium nitrate stopped their growth entirely. 

 The tubercle masses often attain large dimensions. An old 

 woodman on Sir Jonathan Hutchinson's estate at Inval, 

 Haslemere, procured me some roots bearing numerous 

 masses, each 3 inches in diameter. 



Tubercle masses also ,occur on the roots of the Bog 

 Myrtle. They differ in some important particulars from 

 those of the Alder, and though at present the fungus held to 

 be responsible for them is known as Franhiella Brunchorstii 

 (Moller) Ren6 Maire, it will probably be placed eventually 

 in a separate genus, Shibata placed it under Actinomyces; 

 and Pecklo, in 1909, claimed to have isolated an actino- 

 myces-like fungus from the tubercles, which is said to be 



