The Red Colouring of Arctic Plants. 83 
Mycorhiza and its Significance. 
In connection with Stahl’s recent important work 1 on the 
significance of that intimate association of certain fungi with the 
roots of many plants known as “Mycorhiza” (now known 
to be a phenomenon affecting probably considerably more than half 
the species of the higher plants), and his theory that Mycorhiza is 
correlated with a difficulty of obtaining nutritive salts, with feeble 
transpiration, and with poverty or absence of starch formation in the 
leaves, it is of great interest to note, as Dr. Wulff points out ( 1 ) that a 
considerable number of arctic plants have Mycorhiza, (2) that of 16 
species collected and investigated by him all shew marked sugar- 
reaction, 1 and absence or poverty of starch, and ( 3 ) as has been 
already shown, arctic plants have a very feeble transpiration 
current. Though the exact relations of these series of facts is not 
wholly clear, their causal connexion certainly seems indicated. 
Thus the Mycorhiza-symbiosis would fall, at least so far as the 
nature of the soil in which the affected roots live is concerned, into 
two very distinct classes of cases; first, those in which the soil is 
largely composed of humus or leaf-mould, comparatively poor in 
inorganic salts, among which may be mentioned the beech and the 
hazel of our own woodlands ; and secondly those in which the soil 
is quite destitute of humus and while possibly rich in inorganic 
salts cannot supply these freely to the plant owing to the lack of an 
adequate transpiration-current. 
The Red Colouring of Arctic Plants. 
The extraordinary purity and brightness of the colours of many 
Alpine flowers (and the same is true of Arctic ones) is well known. 
The vivid colouring often extends to the whole subaerial part of the 
plant, the leaves and stems shewing a deep red or purple which 
often masks the ordinary chlorophyll-green. This is due to the 
presence of soluble red, purple or blue pigments in the cell-sap of 
various living cells ot the leaf and stem, very rarely (Eriophorum 
(ingustifolium var. triste) to colouration of cell-walls; to these pigments 
the collective name Anthocyanin has been given. Dr. Wulff finds 
that the presence of this pigment is an almost universal character 
istic of Arctic plants. In a very interesting paper published three 
1 Dr. Wulff took precautions against confounding sugar- 
reaction with tannin-reaction. 
1 Der Sinn der Mycorliizenbildung. Jalirb. f. wiss. Botanik, 
xxxiv., 1900. 
