240 AMPLIFICATION AND REDUCTION 
parts of the shoot, z¢er se, and cannot be held to be examples of general. 
reduction. 
There remain to be considered those sporophytes which show some 
form of indirect nutrition, the commonest of which is the mycorhizic 
symbiosis. The occurrence of a symbiotic state is often loosely held 
to be equivalent in itself to a demonstration that the organism in which 
it occurs has been the subject of general reduction; and reference is apt 
to be made in support of this to extreme cases, where it has in fact led 
to. complete saprophytism. But it is necessary to be clear what effects 
they are which necessarily follow upon this habit, as apart from those 
which are occasional and extreme: for it is only the former which can 
properly be counted on for argument. Stahl has indicated that the usual 
structural concomitants of mycorhiza in green plants are such as lead 
to economy of the water-interchange:! viz., a restricted root-development, 
with thick unbranched roots, and absence of root-hairs: little structural 
provision for water-transfer and an absence of organs of water-secretion ; 
while a leathery texture of the leaf, a feature of other plants which 
economise water, is not uncommon. But these characters are by no 
means uniformly or exclusively found in mycorhizic plants: for instance 
Cyathea is mycorhizic, but it shows such characters as the leathery leaf 
less obviously than Asplenium nidus and Osmunda regalis, which are not. 
When present the features above named may be held to be indicative of, 
a probable reduction in respect of the parts immediately affected; but 
that is a very different thing from the general reduction which is some- 
times assumed to follow mycorhiza as a necessary consequence. General 
reduction implies an effect on both the nutritive system and the propagative 
system. But it is to be clearly understood that so far as the mycorhizic 
habit affects nutrition, by yielding as it does in some cases an efficient 
saprophytic supply, the reduction will appear in the vegetative system 
only, and not in the propagative. This is amply illustrated in Phanero- 
gamic plants such as /Veotéia and Sarcodes,? where the flowers and _ fruits 
remain of the usual types though the vegetative system is reduced. 
Similarly, among Pteridophytes, if mycorhiza were really effective in them 
as a considerable means of saprophytic nourishment, we should expect the 
consequent reduction to appear in the vegetative system, with a loss of 
chlorophyll in extreme cases; but that the spore-producing parts should 
remain of the usual dimensions and character of the family: that is, 
supposing the saprophytic supply to be as efficient as the normal chloro- 
phyll nutrition. Now, putting aside certain exceptions to be noted below, 
such a condition is unknown among Pteridophytes, and its absence goes far 
to show that the mycorhizic symbiosis seen in them is not a fully effective 
source of organic nutritive supply. The facts do not bear out the 
general assumption that mycorhizic symbiosis, as seen in certain of 
1 Pringsh. Jahrb., xxxiv., p. 539. 
2See F. W. Oliver, on Sarcodes, Ann. of Bot, iv. 
