292 THE ORCHID REVIEW. 
of Orchis (sic) in the British flora.”—Card. Chron., 1900, XXxviil., p. 217. 
Has it really become quite as bad as this ? 
ARGUS. 
MYCORHIZAS OF ORCHIDS. 
Unber this title appears a very interesting article, by Dr. T. M. MacDougal, 
in the Journal of the New York Botanical Garden (vol. i., p- 7); which we 
venture to repeat. A very important question to cultivators of Orchids is 
involved. It would be interesting to know exactly why it is that certain 
Orchids refuse to grow in our collections—whether it is that the higher 
plant does not receive the proper treatment, or that its ‘“ unseen associate ” 
is labouring under difficulties and gives up the unequal struggle—and we 
hope that Dr. MacDougal will turn his attention to this point.—[ED.| 
“ The roots and underground organs of more than 700 species of Orchids 
have been examined, and all of this number are found to have formed 
unions with fungi in such a manner as to form mycorhizas. A mycorhiza 
consists of the structure resulting from the attachment of the fungus to the 
roots or absorbing organs in such manner that the association results in 
benefit to both. The tube-like threads of the fungus generally gain 
entrance to the roots while they are young, and grow forward, as the root 
extends in length in the tissues just underneath the epidermis. Branches 
of the tubes or hyphz are sent out through the root-hairs into the soil, and 
the two plants work in partnership to accomplish nutrition. The fungus 
takes up the products of decaying leaves and organic matter in the soil, and 
carries them into the root, yielding the greater portion to the higher plant, 
which may actually get all of its food from its minute associate. Some 0 
this food, however, is built up into starch and sugar, which is given back 
to the fungus. The higher plant thus takes the crude material given it by 
the fungus, and makes it into substances which the fungus is unable to 
construct, but which form a very valuable food for it. In addition to this 
advantage to the fungus, the root offers it a habitat in which it is free from 
many dangers it would encounter in the soil. 
“The nicety of attention necessary to the successful culture of most 
Orchids is doubtless due to the fact that, not only must the proper 
conditions of water and temperature be offered the higher plant, but its 
unseen associat? must be provided with exactly the proper soil and food. 
“The fungi which inhabit the hanging roots of the epiphytic Orchids 
bear the same relation to them, though many inexperienced writers have 
described them as parasites. 
‘““By the co-operation of the fungus the Orchid is relieved from the 
fierce struggle to win its food necessary to unaided species, and the great 
