234 EXPERIMENT STATION RECORD. 



The respiration of plants, H. Marshall Ward et al. (Rpt. Brit. Assoc. Adv. 

 8cL, 1904, pp. 344, 345). — A report is given by a committee of the British Association 

 upon investigations by F. F. Blackmail and Miss G. L. C. Matthaei dealing with the 

 effect of temperature and light upon the photosynthesis of leaves. 



It was found that one of the important considerations of the experiments was that 

 the leaves should all be kept under similar conditions of illumination and temperature 

 for some time before the beginning of the experiment, and that the real internal tem- 

 perature of the leaf should be definitely known. With these precautions, a series of 

 experiments was conducted in which the temperatures ranged from —6° C. to 45° C, 

 and it was found that for each temperature a maximal assimilation exists specific to 

 that temperature. 



The amount of light required to produce the specific maximal assimilation varies 

 directly with the magnitude of the maximum. When the maximum is reached no 

 further increase in illumination or in the amount of carbon dioxid supplied will aug- 

 ment the assimilation by the plant. The amount of assimilation is just determinable 

 at —6° C, from which temperature it rises rapidly toward the maximum. At tem- 

 peratures of about 38° C. the leaves are incapable of maintaining their high initial 

 rate of assimilation for any considerable time. The higher the temperature the 

 shorter the duration of the period of maximal assimilation, and it was found impos- 

 sible to obtain the maximal value at temperatures close to 45° C, which was a fatal 

 temperature for the plants under observation. 



The relation between the carbon dioxid assimilation and various intensities of 

 natural illumination was also investigated, determinations being made of the assimi- 

 latory value of natural illumination at dawn, midday, in sun and shade, during rain 

 and storms, and at dusk, and it is shown that the diffuse light of the whole heaven 

 compares favorably with feeble direct sunlight as an illuminant. 



FIELD CROPS. 



Report of the agriculturists, W. P. Brooks, F. R. Church, and S. B. Haskell 

 {Massachusetts Sta. Rpt: 1904, pp. 115-153, dgm. 1). — During this season the general 

 lines of investigation previously described were again followed (E. S. R., 16, p. 350). 

 The experiments this year included 220 plats in the open field, 150 closed plats, and 

 278 pots in vegetation tests. The grass garden of the station includes 48 species and 

 7 varieties, most of them occupying 1 sq. rod of land. 



Potatoes were grown this year in connection with the comparative test of different 

 sources of nitrogen, and on the basis of yield secured the materials ranked as follows: 

 Barnyard manure, nitrate of soda, dried blood, and sulphate of ammonia. Based on 

 the increase in all the crops since the beginning of the experiment, as compared with 

 the check plats, the relative rank of the different fertilizers was: Nitrate of soda 100, 

 barnyard manure 83.6, dried blood 66.9, and sulphate of ammonia 56.9. The grow- 

 ing of soy beans has so far shown but little effect on the succeeding crop. 



This year high-grade sulphate of potash appeared considerably superior to the 

 muriate for rhubarb and cabbage. Silicate of potash gave a relatively very low yield 

 of cabbage and of field and silage corn, while the nitrate and carbonate of potash 

 gave relatively high yields. Results with different phosphates for corn indicated, 

 as in previous years, a very low degree of availability for Florida soft phosphate. 



The soil test with corn has now been in progress for 16 years, and during this time 

 the land has been in corn 8 years and in grass 4 years. Corn was grown in succession 

 the last 3 years, and the past year was excellent on all plats receiving potash every 

 year. The plat receiving muriate of potash alone continuously yielded 47 bu. per 

 acre, and the one receiving dissolved boneblack in addition yielded 53 bu., being a 

 better yield than was obtained on the plat treated annually with 5 cords of barnyard 



