546 



SCIENCE 



[Vol. LV, No. 1429 



research in agriculture looking toward increased 

 production even at the present time when there 

 seems to be an overproduction along many lines ; 

 but also, a plea that agricultural research work- 

 ers broaden the field of their endeavor, and work 

 out new methods of farm management and mar- 

 keting, in order to enable farmers to dispose of 

 their products more readily and at a fair profit. 

 A study of the grasses of Arizona: J. J. 

 Thornber. This paper includes a study of the 

 260 species of grasses of Arizona with compari- 

 sons of the grass floras of New Mexico and Col- 

 orado. The grasses of northern and southern 

 Arizona were compared in numbers, species and 

 the origin of species, typical species of these two 

 grass floras being noted. The grass flora of Ari- 

 zona was stated to consist of 55 per cent, of 

 southern and southwestern species, 25 per cent, of 

 northern species and 20 per cent, of introduced 

 species. The largest genera of grasses in Arizona 

 in order of number of species are as follows: 

 Muhlenbergia, 23 ; Panicum, 19 ; Bromus, 19 ; 

 Bouteloua, 14 ; Sporobolus, 12 ; Aristida, 10. 



Forces concerned in the enlargement of cells 

 during growth : A neju artificial cell : D. T. Mac- 

 DouGAL. The protoplast in its earlier stages is a 

 solid cylindrical or globoid mass of jellies. En- 

 largement or growth in this stage is by the addi- 

 tion of new material and its swelling by the 

 imbibition of water, which constitutes growth by 

 accretion. The formation of cavities or vacuoles 

 in the protoplasm filled with substances which 

 attract water sets up osmosis which pulls in 

 additional water and causes a stretching or en- 

 largement of the entire mass, which is designated 

 as growth by distension. The protoplasmic mass 

 was described as including all substances in tlie 

 cell which may take the form of a reversible gel, 

 that is, which liquefies or dissolves in water or 

 by heat, and which sets or solidifies at low tem- 

 peratures or on dehydration. 



The course of growth of potato tubers: D. T. 

 MacDougal. The growth of potato tubers has 

 been followed in 22 examples measured at Carmel, 

 California, by means of the auxograph. A dia- 

 gram exliibited showed the course of enlargement 

 of the tuber during its development which might 

 cover a period of 60 to 80 days. The highest rate 

 of enlargement of diameter of the tuber was in 

 its earliest stages when it was less than one cm. 

 in diameter. The highest rate of increase in 

 volume, however, ensued at a much later stage, 

 when the tuber had reached perhaps three fourths 

 of its final size. 



An ecological system of -plant relationships: 

 Edith Clements. This is an account of the 

 application of ecological principles to the evolu- 

 tion of flowering plants, as exemplified in the 

 Besseyan system. The evolutionary processes are 

 assumed to be insect-pollination and wind- 

 pollination, and to have brought about funda- 

 mentally similar results by divergent methods. 



Changes of climate and life in the Southwest: 

 Frederic E. Clements. A comprehensive attack 

 upon the problems of climatic cycles in the South- 

 west has disclosed a large amount of evidence 

 drawn from various sources. The most direct evi- 

 dence has been obtained from weather records of 

 rainfall, in following up the clue afforded by 

 Douglass 's studies of tree rings in this region. 

 The operation of larger cycles is indicated in 

 land-forms, such as shore-lines, bajadas and 

 dunes, but is seen with especial clearness in vege- 

 tation. This is particularly true of the Mohave 

 Desert and the Santa Cruz valley at Tucson, in 

 both of which grassland communities exhibit 

 cyclic clmnges in harmony mth those found else- 

 where in the West. 



An improved form of the quadratograph: 

 GOKM LoFTFiELD. The Hill quadrat pantagraph 

 has been greatly improved in the past year. These 

 modifications are described, and the apparatus 

 demonstrated. In addition, the present system 

 of staking and photographing quadrats is dis- 

 cussed briefly. 



Influence of texture on the limit for blacJc 

 alkali: C. N. Catlin. Wheat, barley, milo maize 

 and hegari were grown in soil so compounded 

 from actual field soils as to contain 0.20 per cent, 

 sodium carbonate, the only variable being tex- 

 ture, which ranged from heavy clay to high sand. 

 A table of weights of crops shows the maximum 

 growth in the finer textured soils at this "black 

 alkali ' ' concentration. 



Tlie effect of intercultural practices on tem- 

 peratures and humidity in citrus orchards: E. J. 

 Crider. Comparative meteorological data ob- 

 tained from adjoining cover-cropped and cleanly 

 cultivated citrus orchards in the Salt Edver Valley 

 of Arizona showed that the mean soil temperature 

 of the cover-cropped orchard one foot below the 

 surface was two degrees higher during winter and 

 eight degrees lower during summer than the 

 cleanly cultivated orchard. It was further shown 

 that the mean minimum atmospheric temperature 

 of the cover-cropped orchard was three degrees 

 lower during winter, and the mean maximum 



