1. Twenty -three species of Mucorales have been
isolated from samples of seven soil types. Of
these, twenty are heterothallic species the
remaining three being homothallic.
2. Descriptions of the species are given.
3. The following species have not been isolated befor
from soil in this country:- Mucor hiemalis Wehmer,
Iti!ucor varians Povah, Mucor fragilis Bainier, Mucor
silvaticus Hagem, Mucor albo -ater Naumov, Iaucor.
saturninus Hagen, Circinella Sydowi Lendner,
Rhizopus nigricans Ehrenberg, Absidia c lindrospor
Hagen, Dicoccum asperum Corda, Chaetocladium
Jonesii, Berkeley and Browne Piptocephalis
cylindrospora Bainier, Mortierella tuberosa van
Tieghem.
4. Zygospores have been obtained and described of
Mucor racemosus Moeller, Mucor hiemalis Wehner,
Absidia, cylindrospora Hagen, Zygorhynchus
Vuillemini Namyslowski, Z. Moelleri Vuillemin,
and Piptocephalis cylindrospora Bainier.
5. Two varieties of Z. Vuillemini Namyslowski and a
variety of Circinella Sydowi Lendner have been
isolated and described. On further examination
these varieties may prove to be new species.
6. Generally speaking it has been found that the
positive forms of the Mucorales have a larger
distribution
than the negative in the soil. The
positive mycelia of M. hiemalis have been proved
by experiment to be more resistant to drying than
the negative mycelia.
7. A table has been given for the longevity in culture
of certain of the species.
8. Conditions for zygospore formation are discussed.
9. Perfect hybrid zygospores were obtained in culture
when Mucor varians and the negative form of
M. hiemalis were contrasted and when Mucor
silvaticus and the positive form of M. hiemalis
were contrasted.
10.Imperfect hybridization occurred between the
negative form of Absidia cylindrospora and the
positive form of Rhizopus nigricans.
11.It has been shown that there is no specific
distribution of the Mucorales within the different
soil types. Certain species such as Mucor
hiemalis, M. racemosus and Absidia cylindrospora
have been shown to be of very common occurrence,
having been isolated from practically all types of
soil.
12.The results tend to show however, that all soils
are not equally rich in the number of species of
Mucorales. Soil from a heather moor and from a peat-bog contained fewer species than cultivated
soil.
13. Soil reaction does not affect all the species of
the Mucorales equally. It has been found that
such species as M. racemosus and Zygorhynchus spp.
are able to withstand a very wide range of
Hydrogen ion concentration, while others and
among them are found A. cylindrospora and
M. hiemalis have a more limited range.
