Orchid Mycorrhiza. J. Ramsbottom. 61 
not quite median). The fungus in many of the cells is already digested. 
x 56. 
Fig. 10. Later stage of Odontoglossum showing the beginning of the formation 
of the central stele and root. The stem growing-point is well developed. 
The fungus in the cells is mostly digested. x 36. 
PLATE IV. 
Fig. 11. Protocorm of Vanda showing the young root absorbing its way out 
of the side of the protocorm away from the fungal zone. x 18. 
Fig. 12. Odontoglossum seedling after the formation of the first root. The 
root is not infected from the protocorm. (The dark patches in the root 
are raphides.) x 36. 
Fig. 13. Cells from fungal zone of Fig. 12 more highly magnified. The fungus 
is ‘‘clumped”’ (cf. Fig. 8). A fungal hypha is seen passing through the 
cell-wall. x 215. 
Fig. 14. Longitudinal section of the root of Habenaria near the tip. Digestion 
is more prominent in the older (upper) portion of the root. x18. 
Fig. 15. Longitudinal section of an aerial root of Epidendrum showing in- 
fected cells in the centre and mycelium in the velamen. x18. 
PEALE Vi 
Odontoglossum house; first stages of seedling raising by the ‘“‘pure culture” 
method. 
PLATE VI. 
Odontoglossum house; seedlings one year old grown by the “pure culture” 
method. 
PLATE VII. 
Odontoglossum house; seedlings three and four years old. 
MYCORRHIZA IN THE ERICACEAE. 
By M. Cheveley Rayner. 
There has recently been published a paper by Christoph(:) 
containing an abridged account of researches carried out by 
him on the relations between plant and mycorrhizal fungus in 
the Ericaceae. The species studied were Calluna vulgaris and 
Erica carnea and that part of the investigation with which the 
present critical review deals is concerned with (a) the behaviour 
of “cuttings” of the shoot, and (d) seed cultures of the former 
lant. 
j With the researches on “‘cuttings’”’ I do not propose to deal 
at present as it is hoped that a paper may be ready for publi- 
cation in the near future detailing the results of my own experi- 
ments in the same direction. With regard to the work on seed 
cultures of Calluna, the experimental results recorded by 
Christoph are so remarkably at variance with those published 
in I915(2) and since that time repeatedly confirmed by me, that 
I welcome the present opportunity of discussing them in some 
detail. 
As a starting-point of my own investigations may be taken 
the simple observation that seed of Calluna germinated on 
moist filter paper in a germinator yields seedlings which root 
freely in the seed dishes, the roots showing regular fungal in- 
