THE FUNGUS-ROOT (MYCORRHIZA). 181 
abundant. It is perhaps well to note that during the past six 
weeks (February—March 1923) there has been an abnormal 
fall of rain and very slight frost in the south eastern counties. 
This may account for the abundance of mycorrhiza. A remark- 
able phenomenon was witnessed by members who were present 
at the Club’s Moss Foray on March 17th, 1923. In a hollow 
of considerable size where beech leaves had accumulated there 
was, within an inch of the surface of leaves, a complete carpet of 
mycorrhiza, several layers in thickness. Not a single rootlet 
appeared to be in a normal condition. The exact dates 
given above are of some importance for we have not yet sufficient 
data as to the length of life of mycorrhiza after once being formed. 
McDougall, in describing the result of his investigations, 
writes, ‘“ The primary object from the beginning was to work 
out the seasonal relations of the mycorrhiza of our forest trees.’ 
“Both ectomycorrhiza and endomycorrhiza are normally 
annual. They are formed during the summer, reach their fullest 
development in late autumn, ipa unchanged throughout 
the winter, and die in the spring.’ 
The climatic factor appears to be the chief determining 
one in causing the changes stated above. 
To obtain the mycorrhiza of a birch tree that is growing in 
its customary oak-birch-heath association, all that it is necessary 
to dois to remove carefully to the depth of from one to two inches 
the upper surface of accumulated dead leaves, in which the slender 
root system of the tree is always present. 
Mycorrhiza break off very easily, part with the moisture they 
contain, and shrivel, becoming almost unrecognisable, on being 
exposed to an atmosphere that is at all dry. It is advisable, 
therefore, not to put them into a vasculum with other plants. 
They should be packed in wet moss or put into water in wide 
mouthed bottles of two-ounce capacity. [fat the time of collecting 
they can be rinsed in a pool or stream of slowly running water, 
characteristic points, that it is important to know, as colour, 
shape and size, may be ascertained at once. Other methods are 
required when collecting from trees having a deeper root-system, 
such asoak andhornbeam. With these the soil has to be removed 
little by little to prevent undue injury. A recent writer recom- 
4. Mc.Dougal, W. B.,‘‘ On the Mycorrhiza of Forest Trees.” Americ. Journ. Bot., i., pp. 
51-74 (4 pls.), 1914. 
