Orchid Mycorrhiza. J. Ramsbottom. 59 
ments with these two species. The results of thirteen experi- 
ments are summarized, though the complete account is not 
published. 
Different soils were tried, both sterilized and unsterilized. 
Seeds of Calluna and Erica were sown in these, some having 
their coats sterilized, some being used just as they were taken 
from the capsules. The results were similar in both series of 
experiments, except that Erica carnea germinated only in the 
absence of light. Germination occurred in all experiments, e.g. 
sterilized seeds germinated in sterilized soil. Only those seedlings 
growing in unsterilized soil become infected with fungus whether 
the seeds are sterilized previously or not: in certain cases seeds 
which were taken from capsules in which a fungus was very 
obvious did not give rise to infected seedlings when sown in 
sterilized soil. The author concludes that infection of the root 
always comes from the soil and never from the seed coat. 
Regarding infection in the capsule, Christoph states that so 
long as the carpels are still green and the seed white a fungal 
infection of the tissue can never be observed. 
The author succeeded in extracting the fungus from the roots 
of the plants, but was unable to obtain spores in pure culture 
and was therefore unable to identify it. That it was probably 
the appropriate fungus was shown by infecting seedlings of both 
Calluna and Erica. 
The Ericales are considered to be facultative mycotrophic 
plants, since specimens growing in normal conditions always 
have fungus in their roots. In very dry places, however, plants 
of Calluna vulgaris and of Evica carnea are often without fungi; 
and in pot cultures allowed to become dry the fungus soon 
disappears. 
The third portion of the paper deals with the Pyrolaceae. 
Working with Pyrola uniflora, P. secunda, P. minor and P. ro- 
tundifolia it was found that the hyphae of the infecting fungi 
had clamp-connections (and were therefore probably Basidio- 
mycetes). The conclusion reached is that here also no true 
“symbiosis” exists—infection depends upon many external 
factors, of which temperature, soil, moisture and aeration are 
the chief. Coralloid roots are not brought about by infection: 
there is a special development of the large epidermal cells and 
these, owing to their function of absorption, are specially suited 
for fungal development. 
In Monotropa the fungus possesses no clamp connections. 
_ The author was successful in germinating seeds of Pyrola 
rotundifolia which he chose, as they were the largest of the four 
species. The best results were obtained from: 1. Strong concen- 
trated soil-extract. 2. Addition of peptone solution. 3. Sowing 
