ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 219 



to a far less, but appreciable extent ; while absorbed salts of barium do 

 not reach the stem at all. It follows that the less the molecular weight 

 of the base the further the salts mount into the stem. The barium salts, 

 on the other hand, accumulate in the root much more considerably than 

 the others. 



Cryoscopic Determination of Osmotic Pressure in certain Plant- 

 organs.* — W. R. Gelston Atkins draws attention to the importance of 

 osmotic pressure in relation to the vital functions of the living cell, 

 emphasizing the evolutionary aspect, the earliest organisms being water- 

 dwellers. The present paper forms one of a series of records aimed at 

 discovering the relation between the osmotic pressure and the general 

 metabolism in selected plants, and deals with fleshy organs — fruits, rhubarb 

 stalks, artichoke tuber, etc. The osmotic pressure P is calculated from 

 observation of depression A in the freezing-point of the sap, from the 

 equation P = 12*03 A, the temperature being 0° C. The predomina- 

 ting substances in the sap, further, may be ascertained roughly from the 

 mean molecular weight (M) ; and this has been ascertained in many 

 cases by evaporating a weighed quantity (not more than 3 grm.) of 

 filtered sap in a steam-oven until a constant weight is obtained. The 

 weight of the solvent being I — viz. weight of sap less weight of solids, s, 

 and k being the constant for the molecular lowering of the freezing-point 



of the solvent, we have M =- x — 



The pressures recorded range from 5 ' 94 atm. (fruit of Lycopersieum 

 esculentum) to 29*53 atm. (fruit of Pyrus communis). Rubus Idaeus, 

 with pressure of 9 - 26 atm., represents a mean of pressure for many ripe 

 berries. 



Interesting details and a table of results are given. As the result of 

 over fifty measurements, the author concludes that similar plant-organs 

 of the same species have approximately equal osmotic pressures ; but this 

 does not apply to leaves. The mean molecular weights in the case of 

 fruit ranged from 110 {Lycopersieum esculentum) to 231 {Citrus Auran- 

 tium). In the case of underground organs the pressure ranged from 

 6* 5 atm. {Solarium tuberosum) to 18'7 atm. {Helianthus tuberosus), and 

 the mean molecular weight from 101 {Brassica Rapa root) to 391 {Heli- 

 anthus tuberosus), the highest figure determined. The red stem of 

 rhubarb gave the lowest recorded mean molecular weight 76, with 

 osmotic pressure of 6*52 atm. 



Regeneration and Polarity of Plant-organs. f— J. Doposcheg- 

 Uhlar's account is well illustrated by reproductions from photographs. 

 Dealing first with Ferns, it is established that the shoots regenerated 

 from a seedling, from which the growing-point has been removed, 

 develop in the same way as youug plants arising from a fertilized arche- 

 gonium. The shoots usually arise exogenously, but exceptionally endo- 

 genously. " Regenerates " from internodes in the Ferns display a similar 

 development. They may arise exogenously below the epidermis, or near 

 the surface of the callus formed on the cut surface. If bud-shoots be 



* Sci. Proc. Rov. Dublin Soc, xii. (1910) pp. 4G3-9. 

 t Flora, cii. (1911) pp. 24-86 (figs.). 



