raceme varies in the different species from an almost solid head, as 

 seen in Plate I, to a very loose, elongated panicle, there being a con- 

 siderable range of variation in the inflorescence within the limits of 

 the same species. The perianth is spreading, withering-persistent, 

 the sepals bearing one or two glands near the base. The stamens are 

 free or attached to the bases of the segments. The capsule is three 

 lobed and dehiscent to the base in maturity. 



The species of Zygadenus are spring and summer plants. On 

 May 8, 1913, in the neighborhood of the Greycliff station, Mont., 

 Z. venenosus was about 4 inches high, the largest plants not exceeding 

 6 inches, and the flower scape was not visible. On May 11 the plants 

 were in bud, and they blossomed through -the month of June. Seeds 

 were formed the last of June and early in July, and after the middle 

 of August the plants had largely disappeared. 



Zygadenus elegans was in full blossom near Red Lodge, Mont., on 

 July 20, at an altitude of approximately 6,000 feet. In 1910 Zyga- 

 denus coloradensis was in blossom in Colorado at about the same 

 time (July 20) at an altitude of about 10,000 feet. 



In Montana, Zygadenus venenosus grows typically at lower levels 

 than Z. elegans. As stated by Chesnut, its favorite habitat is in the 

 shallow ravines occurring on hillsides. It does not grow abundantly 

 on dry hillsides nor in wet ravines, but it is very commonly found 

 in the shallow depressions on the north slopes of bench lands. Z. 

 elegans grows at higher levels (Rydberg gives as its limits 6,500 to 

 12,500 feet) and in locations where more water is available than is 

 necessary for Z. venenosus. While it grows readily on hillsides, it 

 reaches its best development in size in distinctly wet places, some- 

 times immediately in contact with rivulets. 



In - California and Oregon, Zygadenus venenosus grows in the 

 meadows, while Z. paniculatus grows upon the hillsides. Z. veneno- 

 sus is more common on north slopes and Z. paniculatus on south 

 slopes. 



The species of Zygadenus may grow as more or less scattered indi- 

 viduals, but sometimes they are massed together in large areas, 

 including, perhaps, several acres, in which, at the time of flowering, 

 they seem to be the principal vegetation and give a characteristic 

 greenish yellow color to the landscape. 



The species of Zygadenus are distributed very widely in the United 

 States and are found as far north as Alaska. They occur most 

 abundantly from the Rocky Mountains west to the Pacific, and their 

 importance as stock-poisoning plants is confined almost entirely to this 

 part of the United States. Plate I shows the general appearance of 

 Zygadenus venenosus. This is an Oregon plant and shows the flowers 

 as they appear at the beginning of blossoming. Later, the raceme is 



