168 MASSACHUSETTS AGRICULTURE. 



specimens, although but little distorted in shape, were seen to 

 be diseased, by the black color of the interior, which could 

 readily be seen through the nearly transparent outer portion 

 of the leaf. When split in two, it was plain that the outer 

 and larger leaves were more diseased than the inner ones, 

 some of which, as far as the naked eye could detect, seemed 

 sound. The specimens which were received early in June 

 had attained a height of from six to eight inches, but the bulb 

 was not more than half or three-quarters of an inch in diame- 

 ter. The outer part of the leaves had broken open, and the 

 inside was seen to be composed of a stringy mass, covered 

 with black powder. In some places almost all traces of the 

 leaves had disappeared, nothing remaining but a shapeless 

 mass of black dust, held together by a few threads. Where 

 the leaves were comparatively sound, the epidermis was rupt- 

 ured in streaks, which ran parallel with the length of the 

 leaf. The young bulbs were marked on the outside with 

 black streaks, which were smaller than those on the leaves, 

 and some of the inner coatings were streaked, while others 

 were comparatively sound. Fig. 4, frontispiece, represents a 

 young plant where the disease is not very far advanced, and 

 the epidermis is ruptured, showing the black smut inside. 



A microscopic examination of the black dust shows it to 

 consist of spores, characteristic of the genus Urocystis. Three 

 such spores are seen in fig. 5. Each spore consists of a single 

 dark round central ceil, the spore proper — rather rarely of 

 two cells — surrounded by a number of small cells of a lighter 

 color and thinner substance, each one being flattened on the 

 side where it is in contact with the spore proper. The term 

 applied to the smaller bodies is accessory spores, the neben 

 sj)oren of German writers. A microscopic examination of 

 the threads show a mixture of the tissue of the onion with 

 the mycelium and spores of the Urocystis. 



Returning to the leaves, which appear nearly sound, we 

 find, at the distance of one or two inches from the black 

 spots, that the tissue of the leaf is invaded by the mycelium 

 of the Urocystis. It is most abundant near the vessels of the 

 leaf, extending in tangled masses upwards and downwards, 

 and giving off branches which run outwards, parallel to one 

 another. Until the disease is far advanced, the outer portion 



