An investigation of the Mucorales in the soil

Abstract

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.