32fi EXPERIMENT STATION RECORD. 



lu'iir Tucson. Ariz., and withiu the limits of tlie laboratory domain and tliat 

 part of the valley immediately adjacent 12 plant associations have been recoR- 

 nized and defined. Tliese naturally fall into 4 groups corresponding with the 

 main t()iu>t;rai)liical features of the area under observation. 



The observations made in this area, supplemented by comi)aratl\e studies in 

 the Gila Valley and elsewhere, have led to the conclusion that soil properties 

 and aspect are of p:iramount importance in determining the local distribution 

 of desert plants. AVith regard to the former it has been learned that soil water 

 exercises a controlling influence, but that for certain species aeration and the 

 percentage of alkali salts are also important. 



Peculiarities of structure and habits, correlated with water supply on the 

 one hand and temperature relations on the other, are exhibited by a large 

 percentage of plants of the laboratory domain, and these structures and habits 

 are lielieved to have determined and to be still determining the existence of 

 the species in places where they are now growing. 



On the g'ermination of old and mutilated seeds, L. Macchiati {Bill. Soe. 

 Bot. Itah, 1!)08, No. 7-9, pp. L'ft-lol). — Experiments are reported on the germi- 

 nation of seeds of maize, barley, millet, chick-peas, and beans, in which old seeds 

 were contrasted with those of the crop of 1907. 



At temperatures ranging from 9 to 17° C, with a daily temperature at 3 p. m. 

 of 12 to 16°, 18 per cent of maize, 51 of barley, 70 of millet, 22 of beans, and 

 23 of chick-peas germinated in 3 weeks when the seed was fresh, while of the 

 old seed only 7 per cent of maize, 5 of barley, and 12 of millet germinated. 

 None of the old leguminous seed sprouted and of the nongerminating seed the 

 legumes were the first to rot. Where the temperature was increased to 20 to 

 24° the fresh seed gave the following germinations: 86 per cent of millet, 96 of 

 maize, 100 of barley and beans, and 97 of chick-peas, while the old seed did not 

 show any considerable increase. 



In studying the effect of mutilation on germination it was found that one or 

 both cotyledons of the leguminous seeds and one-half to two-thirds of the 

 endosperm of grains could be removed without preventing the germination of 

 the seeds when placed in favorable conditions. In some instances mutilation 

 seemed to hasten germination. 



The influence of seed bed on the amount and uniformity of germination, 

 F. MuTH Uahresher. Ver. Angeiv. Bot., 6 (1908), pp. 152-222, fig. i).— The 

 author has studied the influence of the seed bed on the germination of a large 

 nimiber of seeds, testing filter paper, a yellow clay seed bed, and 2 forms of a 

 white clay seed bed. The germination of the different kinds of seed in the 

 different seed beds is given at length. 



The author finds that filter paper is best for the germination of French rye 

 grass, alfalfa, spurry, hemp, parsnip, rape, mustard, fennel, onions, and garden 

 beets. The yellow earthenware seed bed seems to be adapted to English rye, 

 fescue, barley, oats, wheat, white clover, alsike clover, tobacco, flax, white pine, 

 common pine, fir and larch, while the white clay seed bed was preferred for the 

 germination of timothy Italian rye grass, redtop, orchard grass, red clover, 

 crimson clover, serradella, vetch, cress, field spurry, buckwheat, etc. 



The relation between the intensity of respiration and the germinative 

 ability of seeds, (). K. Hausmann and 11. P. Iwanissowa {Isv. Imp. »S7. Pctcrh. 

 Bot. Sada (Bui. Jurdin Imp. Bot. St. Petcrsh.), 9 (1909), No. 5, pp. 91-lOii).— 

 The author has reported upon experiments made to test the method proposed 

 by Qvam (E. S. R., 17, p. 860) for the determination of the germinative ability 

 of seeds. He found that while there was undoubtedly a relation between the 

 respiration and germination of seeds, the connection was not sufficiently close 



