AGRICULTUEAL BOTANY. 849 



From ti xperiments the author concludes thai total transpiration of wheat 



plants grown in various media is as good a criterion for comparing the relative 

 growth in these media as is the weighl of the plants. The amount of transpira- 

 tion is practically a simple function of the leaf surface, and this varies with the 

 leaf weight, which in turn varies with the weighl of the entire tops. Thus it 

 is believed thai total transpiration Is a measure for the growth of the plant. 



It is held thai the nature of the s-oii or solution In which the roots are grown 

 has little or oo influence on those structural and physiological properties of the 

 leaves which control the amounl of water losl per unit of leaf surface; In 

 making us.- of this criterion of transpiration for the coi 



nutrienl dia, the author says thai it must In- borne in 



occur variations which appear to be unexplained. < >n th 

 the number of plants used the nearer the results will appr< 



It is shown ;ils<» thai temperature, atmospheric condition 

 transpiration, and these factors must be considered in i 

 kind. 



The methods for comparison of planl growth provisionally established for 

 wheal are said to hold good for grasses generally. 



The development of root hairs, Laktitia M. Snow (Bot. da.:., \0 (1905), \<>. 

 /. pp. I .' '(8, pi. I. figs. 6). The author reports investigations on the causes for 

 the production of root hairs, preliminary experiments being made with ;i large 

 number of plants and detailed investigations carried on with seedlings of 

 wheat, corn, pen. and squash. 



The effeel of various factors in determining the development is shown, the 

 author stating that lighl and darkness appear to have an indirect effeel through 

 their influence on growth. High temperature with sufficient moisture decreased 

 the production of root hairs with an increased elongation of the internal cells. 

 The slower the growth of the roots the hotter the development of the root hairs. 

 Retardation of growth by glass tubes, wounding, or resistance favored root 

 hair production. 



The roots of corn seedlings in water first assumed a curled condition, produc- 

 ing abundanl root hairs, hut Inter they grew straight and smooth, either on 

 account of accommodation to the oxygen supply <»r because thai gas was sup- 

 plied through the aerial parts. A saturated atmosphere with high temperature 

 tended to suppress the development of hairs, and a saturated soil showed a simi- 

 lar effect on corn and wheat seedlings. Curves and swellings on roots had a 

 favorable effect upon the development of root hairs, probably on account of the 

 retardation of t he growth of the root. 



The examples of retardation favoring root-hair development showed that it 

 was not the rate of growth hut the differential elongation of the inner and outer 

 cells that was the important factor. Root-hair production seems to depend en 

 the ratio between the capacity of the epidermal cells to elongate and their 

 ability to do so. and the activity of the epidermis may he in inverse proportion 

 to the activity of i he central cylinder, lateral roots appearing when the root 



hairs are suppressed. 



A bibliography of literature relating to this subject is appended. 



Agricultural microbiology, E. Kayseh I Wicrobiologie Agricole. Paris: J. /.'. 

 Bailli&re & Sons, 1905, />/>. XXI+440, figs. iu<>). In the introductory pari of this 

 hook the author describes in a general way micro-organisms and the effects of 

 physical and chemical agents upon their development, after which he takes up 

 the r.Me which they play in soil fertilization, describing their distribution through 

 the soil, their action on manures, nitrification and denitrification, fixation of 

 atmospheric nitrogen, etc. 



