AGKICULTUKE AT THE AMERICAN ASSOCIATION. 525 



lisin. i. c. th(> total solids less the salt, which can be easily determined 

 by estiniatiiio- the salt. The author gave the factor or coefficient which 

 he has worked out. 



A paper by A. S. Loevenhart on Some Observations on the Rennin 

 Coaoulation of Milk, which was presented before the American 

 Physiological Society, may ))e mentioned here. It was explained that 

 in the rennin coagulation of milk there is a stage when the milk may 

 yield a heat coagulum before there is any apparent change in the con- 

 sistency of the milk. The interval ])etween this metacasein stage and 

 the syjontaneous coagulation varies inversely with the amount of rennin 

 present; it may be so transient as to he imperceptible, or it may be 

 indetinitely prolonged by an}^ agency w hich partially tixes the calcium, 

 as boiling, adding a little ammonium oxalate, etc. Large amounts of 

 anunonium oxalate entirely prevent any heat coagulation at this stage, 

 indicating that soluble calcium salts are necessary for the metacasein 

 reaction. If the rennin be destroyed by heat at that stage, a coagulum 

 will be produced by the addition of calcium chlorid. indicating that 

 the caseinogen has been largely transformed into paracasein. Fresh 

 milk can not precipitate paracasein solutions nor can it prevent the 

 pi-ecipitation of paracasein by calcium chlorid. These facts led the 

 author to conclude that the calcium salts in milk are altei'ed in some 

 way during the action of the rennin, and by virtue of this become 

 capable of precipitating paracasein. It was suggested as most prob- 

 able that the calcium salts of the milk are very loosely combined with 

 some constituent of the milk, and that these compounds are dissociated 

 during the action of the rennin. 



BOTANY. 



The botanical papers of agricultural interest were about equally 

 divided between the section of botany of the Association, the Botan- 

 ical Society of America, and the Society of Plant Morphology and 

 Physiology. Isolated papers on botanical subjects were also read 

 before other sections and societies and are here included. There were 

 many others of general interest to botanists but not of sufficient direct 

 bearing on agricultural science to be included in this review. 



In his vice-presidential address before the section of botany, D. H. 

 Campbell took the subject of the Origin of Terrestrial Plants. The 

 various factors influencing the development of terrestrial plants were 

 stated to be food, water, and various modifications of the reproductive 

 plant organs. Of these factors the speaker held that water was one of 

 the prunary factors in determining whether a plant should be aquatic 

 or terrestrial. The progressive development of plants from aquatic 

 through amphibious to terrestrial habits was traced. 



J. C. Arthur, retiring president of the Botanical Society of Amer- 

 ica, delivered an address on Problems in the Study of Plant Rusts. 

 16398— No. 6—03 2 



