AGRICULTURAL BOTANY. 527 



leaves, roots, aud fruits of about 2 dozou si)ecies of plants to deteriuiue the 

 osmotic pressures from the freezing points of the saps. Most of the experi- 

 ments were carried on with the common lilac (Syringa rulf/aris). 



It was found that osmotic pressures vary with species aud individuals, but 

 that leaves of the same individual under similar conditions have the same 

 osmotic pressure. Under varying conditions, as in the case of the lilac, tlio 

 pressure in the leaves was found to vary from 24.,^)S to ll.GS atmospheres. The 

 variation in pressure was not limited by the height of the leaves above the 

 ground, nor by the resistance of the conducting tracts supplying the leaves. In 

 each case the osmotic pressure was much greater than the tension of the water 

 supply could have been. 



The variations in the osmotic pressure observed are believed to have been 

 due principally to fluctuations in the carbohydrate contents of the ceils. A 

 similar, but smaller, rise in pressure was observed in i)lucked leaves stored in 

 the dark, the changes in this case being probably due to the hydrolysis of sac- 

 charose and starch. In starved leaves or in roots kept in the dark no such rise 

 was observed. Shielding the leaves from light was found to reduce greatly the 

 osmotic pressure in leaves still attached to the plant, and mature leaves, other 

 things being equal, showed a higher osmotic pressure than developing ones. 



In all the roots examined the osmotic pressure was comparatively low, only 

 from 4 to G atmospheres. 



The greatest depression of freezing point recorded was with the sap of the 

 lilac, which corresponded to an osmotic jjressure of 26.S7 atmospheres. The 

 smallest depression was in the sap of Cham(erops humilis, which amounted to 

 only 3.79 atmospheres. 



The high figures given for the lilac are not believed to be the maximum 

 osmotic pressure for this plant. It was found that assimilation and evapora- 

 tion could raise the osmotic pressure of leaves before wilting. In summer, 

 when the leaf cells are loaded with greater quantities of sugars, the wilting 

 concentration will be higher, and in this case it seems probable that pressures 

 of from 30 to 40 atmospheres may be found in the lilac. 



The forination of albuminoid substances in plants, N. I. Vasilev (Trudui 

 Mendclyersk. Syczda Obshch. 1 Prikl. Khim., 1 {1907), pp. Ji02~40.',; ubs. in 

 Zhur. Opuitn. Agron. (Russ. Jour. E.rpt. Landic), 10 (1909), No. 5, pp. 703, 

 704). — Among the more important facts established by the author were the 

 following : 



An increase in albuminoid nitrogen takes place at the expense of asparagin 

 in pods of lupines when separated from the plant, whether they are kept in 

 darkness or in the light. There was an evident transfer of albuminoid sub- 

 stances from the ixhIs to the seed, and it seems probable that some of the amido 

 acids are converted into asparagin, which in turn is used in the formation of 

 albuminoid materials. In general the other organic bases were found to have 

 a role similar to that of the amido acids. The seeds showed such an increase 

 in the total albuminoid material that in addition to the proportion obtained 

 from the pods there must have been a utilization of the crystalline nitrogenous 

 compounds in the seeds. A constant decrease in asparagin and amido acids was 

 found to take place with the increase in ail)uniinoids. 



The effect of certain hydrolyzable salts on plants, A. (Jregoire (Bill. ^oc. 

 CJiim. Bcly., 2-'i {1910), No. ',, pp. 200-209, pj. 7).— In order to determine the 

 effect of readily hydrolyzable salts on plant growth the author conducted a 

 series of water cultures with rye. testing the comparative effect of a liumate 

 of silica and calcium, precipitated calcium carbonate, sodium zeolite, and cal- 

 cium zeolite. These salts were chosen as they commonly occur in soils. 



