THE ONION-SMUT. 175 



NOTE. 



Inasmuch as the fungus causing the smut has not,* as far as we know, 

 been as yet scientifically described, a word or two on its botanical rela- 

 tions will not be out of place. The species of Urocystis are distinguished 

 principally by the characters of the spores, which consist of spores proper 

 and accessory spores. The onion-smut may be described as follows :— 



Urocystis Cepul/e.— Frost, mscr. Spores globular, from .0012 mm. 

 to .00155 mm. in diameter, composed of, generally, one, occasionally of 

 two, dark brown spores proper ; surrounded by numerous, twelve to twenty, 

 accessory spores. Germination unknown. Mycelium, about .00018 m.m. 

 in diameter. In leaves and bulbs of cultivated onions. Spring and early 

 summer. 



This species differs from Urocystis occulta and U pompholigodes in the 

 smaller size of the spore masses, the spores proper being generally single 

 instead of united by twos and threes, and in the smaller size and usually 

 greater number of the accessory spores. 



In recent times a discussion seems to have arisen as to whether the 

 species of Urocystis should be considered as related to the Uslilacjineoz, or 

 rather as mere sclerotioid forms of unknown species. The present state 

 of mycological science would hardly seem to justify any pronounced 

 expression of opinion. Accepting, however, the excellent observations 

 of Wolff on the germination of the spores of Urocystis occulta, we must 

 confess that the formation of the spores in Urocystis hardly seems to jus- 

 tify referring the genus to the Ustilaginea', even if the germination points 

 in that direction. On the other hand, if we may judge by Urocystis Ccpula-, 

 to consider the genus a form of sclerotium hardly seems allowable. 



An examination of the mycelium of the onion-smut shows the follow- 

 ing manner of formation of the spores : There first appears a small lateral 

 swelling of the hypha, which divides by a partition at right angles to the 

 length of the hypha into two cells, or else, as is not unfrequently the case, 

 the two cells arise from the hypha simultaneously and close to one another. 

 Figs. 1 and 2. Of the two cells which thus arise, one enlarges so as to 

 become nearly spherical, whilst the other elongates into a worm-like 

 body which bends over the surface of the other cell. In a shoi-t time the 

 worm-like thread is divided into a number of cells by partitions at right 

 angles to its length. Fig. 3. The cells into which the worm-like body is 

 thus divided then bud out at the sides and grow down in a winding man- 

 ner so as to cover the original globular cell. By subsequent division of 

 these winding cells the accessory spores are formed. This process, in its- 

 initial stage, reminds one of what takes place in Podospha;ra. There is 



* In the Report of the Agricultural Department, Washington, 1872, p. 193, is a 

 short notice of the onion-smut, accompanied by a figure in which, amongst other 

 objects, some spores of Urocystis Copula are represented. The accompanying descrip- 

 tion is, where not hopelessly confused, entirely incorrect. The fungus is called a 

 Peronospora; to which genus, however, the figures do not bear the least i-esemblance. 

 It would be quite impossible to recognize the fungus from the description given. 



