198 RESEARCHES ON FUNGI 



conjugate nuclei and never exhibits karyogamy or any other signs 

 of sexuality. 



The vegetative cells of Sporobolomyces, in their form and mode 

 of vegetative multiplication, resemble those of the Saccharomycetes ; 

 but, whereas in Sporobolomyces the spores are produced as conidia 

 on aerial sterigmata, in the Saccharomycetes the spores are pro- 

 duced inside the mother-cells as ascospores. This striking difference 

 in the mode of spore-production clearly indicates that Sporobolo- 

 myces is not closely related to the Saccharomycetes. 



Yeast-like budding occurs not only in the Saccharomycetes, but 

 also in Mucor, Exoascus, Ustilago, etc., and by itself is of little or 

 no value in determining the systematic position of the fungus 

 concerned. 



As a result of a long series of investigations made on living fungi 

 I have become convinced that, in the Basidiomycetes, in every 

 species in which basidiospores are discharged (all Hymenomycetes, 

 all Uredineae, and all species of the genus Tilletia), normally every 

 spore without exception is developed asymmetrically on the end of 

 a conical sterigma, has a tiny excretory spore-hilum on one side of 

 the top of the sterigma and, as soon as it is ripe, is violently dis- 

 charged by the drop-excretion mechanism. 1 



Since the mode of development and discharge of the basidiospore 

 in all Hymenomycetes, all Uredineae, and all species of Tilletia is 

 identical, one is justified in drawing the conclusion that it is a funda- 

 mental character of the basidiospore which has been inherited from 

 the common ancestor of the Hymenomycetes, the Uredineae, and 

 the Tilletiaceae. 



In the Gastromycetes 2 and the Ustilaginaceae, the basidiospores 



1 The data from which this conclusion has been drawn are specially treated of : 

 for the Hymenomycetes in Vol. II, Chapter I ; for the Hymenomycetes and Uredi- 

 neae together in Vol. Ill, Part II, Chapter I (p. 497 et seq.) ; and for Tilletia in this 

 Vol. V. Illustrations showing the structure of the basidiospores, the drop excreted 

 at the spore-hilum, and the discharge-of the basidiospores are given : for the Hymeno- 

 mycetes in Vol. II, on pp. 7 (Fig. 2), 10 (Fig. 3), 12 (Fig. 4), 13 (Fig. 5), 14 (Fig. 6), 

 16 (Fig. 7), 18 (Fig. 8), 19 (Fig. 9), 290 (Fig. 97), 338 (Fig. 121), 429 (Fig. 147), and 

 in Vol. Ill on pp. 220 (Fig. 93), 227 (Fig. 95), 252 (Fig. 107) ; for the Uredineae in 

 Vol. Ill, on pp. 503 (Fig. 203), 505 (Fig. 204), 508 (Fig. 205), 511 (Fig. 206), 537 

 (Fig. 216) ; and for Tilletia in this Vol. V, on pp. 222 (Fig. 108) and 232 (Fig. 114). 



2 For a discussion of basidial degeneracy in the Gastromycetes vide these 

 Researches, Vol. II, 1922, pp. 29-33. 



