GALLS CAUSED BY FUNGI 
XI 5 
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.) Rene 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 /^ccur 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 Frankiella Brunchorstii 
(Moller) Rene 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 
