428 ' TwivXTY-EiGiiTH Annual Report 



death camas. Specimens of the plants sent for examhiation proved 

 to be a species of Zygadcnns. Some sheep and a fe whorses were 

 reported poisoned from eating lupines near Prescott. The speci- 

 mens examined showed an abundance of the seed pods which are 

 the parts of hipines that are most poisonous. At Snowliake, Shuai- 

 way and Springerville, Arizona, water hemlock or water parsnip 

 {Ciciita occidcntalis) was found growing occasionally in irrigation 

 ditches. At Greer, a few miles above Springerville, Arizona, it was 

 growing in great abundance in the Little Colorado River. This 

 species has not been reported heretofore from our State ; it is one 

 of the most deadly of our poison plants. Every effort should be 

 made to keep irrigation ditches free from it, otherwise losses of 

 stock are certain to occur in the irrigated valleys. 



WEATHER CONDITIONS AS AFFECTING PLANT 



GROWTH 



The winter of 1916-1917 was unusually cold throughout, though 

 at no time did the temperatures drop extremely low. The ther- 

 mometer at the University grounds registered temperatures below 

 32 degrees F. on 48 nights from November 8, 1916, to April 2, 1917, 

 inclusive, or an average of one out of every three nights for this 

 period of nearly five months. December was the coldest month 

 and December 11th the coldest night wdth a minimum of 15 de- 

 grees F. There were 18 nights in December when the temperature 

 dropped below 32 degrees F. At the University Farm in the Rillito 

 Valley, four miles north of Tucson, the minimum temperature was 

 9 degrees F. As was expected, the temperatures there were gener- 

 ally lower and the number of nights greater when the temperature 

 dropped below 32 degrees F., than at Tucson. A considerable 

 amount of damage was done to tender exotic trees and shrubs 

 throughout southern Arizona, though this was much less than that 

 done during the winter of 1912-1913, when the temperature dropped 

 to 6 degrees F. 



The following ornamental trees and shrubs on the University 

 grounds and in Tucson were more or less injured. The first seve.i 

 of these were severely frozen back and the remaining ones were 

 moderately to slightly injured. (1) Australian silk oak {Grevillea 

 robusta) ; (2) flame tree {StcrcuUa accrifoiia) : (3) Brazilian pepper 

 (Schinus terehinthifolius) ; (4) Satsuma orange {Citrus sinensis) ; 

 (5) Japanese kumquat (Citrus jaf^ouica) ; (6) Burbank's spineless 



