Perennial Dodder: An Additional Note. 



65 



to obtaining further data in the matter, the writer carried on a 

 series of porous cup atmometer readings in the Selkirks during 

 the past summer. These mountains are heavily forested and 

 altogether they much resemble the Alps. The instruments were 

 safeguarded and checked in ways which seem to put part, at 

 least, of the results beyond question; the season was unusually 

 favorable, being dry and warm. One series of instruments was 

 in continuous operation twelve weeks. The results as a whole 

 seem impossible to harmonize with the idea that total evapora- 

 tion increases with altitude. The maximum in each case was 

 shown by the pair of instruments at the second station, 1,100 

 meters altitude. Above that a gradual and irregular diminu- 

 tion was shown. Possibly the standard writers may have over- 

 looked the part played by temperature, for this, too, is a 

 factor in the evaporation rate and might overbalance the effects 

 of diminished pressure and movement. It must be kept in 

 mind that the results mentioned refer only to weekly totals and 

 throw no light on what might happen during a certain portion 

 of the day. It will naturally be remembered, too, that the 

 problem of the plant is to maintain a balance between water 

 supply and water loss. If cooler soil or any other circumstances 

 makes the obtaining of water more difficult, then the same or 

 even a diminished evaporation rate might demand increased 

 resistance to evaporation on the part of the plant. 



PERENNIAL DODDER: AN ADDITIONAL NOTE. 



By Francis E. Lloyd. 



A few months ago I reported in the Plant World that a 

 species of Cuscuta to be found in N. Zacatecas, Mexico, passes 

 the winter in a semi-dormant condition on the host plant. A 

 recent bulletin from the N. Y. Agricultural Experiment Station 

 (No. 305) has just been received, in which it is noted by Stewart, 

 et al y that a species of cuscuta which affects the alfalfa in that 

 state "lives over winter in New York alfalfa fields on alfalfa, yel- 

 low trefoil, red clover, dandelion and daisy fleabane." Inasmuch 

 as the species in question "does not commonly produce seed in the 

 New York alfalfa fields," the perennating habit is of paramount 

 importance to the dodder. The authors observe that this is 



