Ju.xE 23, 1905.] 



SCIENCE. 



939 



through the stimulative action of external 

 agents. It was determined in this ease 

 that in general no absorption of the sub- 

 stances bathing the plant occurs ; therefore, 

 osmotic substances are produced within 

 the cell and largely by increased concentra- 

 tion of the normal organic cell products. 

 The extent and method of this capability 

 for turgor regulation are highly important, 

 as is also the general question of the rela- 

 tion of turgor to growth. In recent times 

 some of the important problems in this 

 connection have been well suggested by the 

 work of Ryssleberghe, Puriewitsch, Over- 

 ton, Copeland and Livingston. 



The absorptive systems of plants seem 

 to be admirably adapted for their needs 

 from a diosmotic point of view. Diffusion 

 maj', therefore, be sufficiently rapid to sup- 

 ply all demands of the absorbing cells or 

 organs. Nevertheless, the assumption that 

 ordinarily diffusion through the cell and 

 plasmatic membrane is sufficiently rapid 

 properly to provide for the translocation 

 of metabolic products from cell to cell is 

 certainly open to further inquiry. Present 

 knowledge of the translocatory processes is 

 insufficient. Plasmatic connections between 

 cells are now known to be of common oc- 

 currence, and this fact has given further 

 interest to the above inquiry. Brown and 

 Escombe are of the opinion that the plas- 

 matic connections are eminently adapted 

 for all of those phenomena which they 

 have found tb belong, as subsequentlj' men- 

 tioned, to multiperforate septa. They 

 claim, further, that with slight differences 

 of osmotic pressure the necessary concen- 

 tration of gradient for increased transloca- 

 tion would be very simply eff'ected. 



Thus far it has been difficult to throw 

 any light upon cell-absorption and selection 

 in many complex natural relationships by 

 calling in the assistance of the dissociation 

 theory and the ionic relationships of the 



salts in the soil. The external relation- 

 ships of nutrient salts, or the relative 

 abundance of these in substrata supporting 

 vegetation, constitutes a problem with 

 which the physiologist must be concerned. 

 It is only necessary to glance at the results 

 of work done by various experiment sta- 

 tions in this country to be convinced of 

 the great physiological importance which 

 may be attached to such studies. 



Recent results tend to emphasize the 

 importance of considering to a greater de- 

 gree the physical conditions of the soil. 

 Some have even gone so far as to claim 

 that practically all soils contain a sufficient 

 quantity of plant food; and that the all- 

 important question is the regulation of the 

 water supply in accordance with the qual- 

 ity of the particular soil. This latter, 

 however, is an error into which few phj'si- 

 ologists ha^'e fallen. Nevertheless, precise 

 studies upon the relation of plants to the 

 physical charaetei's of soils afford prob- 

 lems which should receive the best atten- 

 tion, ^lany of the problems are not new, 

 and in a qualitative way, at least, the prob- 

 lem of the relationship of the conservation 

 of moisture, and the tilth of the soil to 

 productiveness has been duly appreciated 

 by the best agronomists. AVe must notice 

 with regret, therefore, that botanists have 

 not always appreciated the importance of 

 such work. Either directly or indirectly 

 the water factor is a chief one in regulating 

 the activities of the living plant and must 

 be considered from every possible point of 

 view. 



It may, perhaps, be less a problem than 

 a routine matter to determine the relation 

 of the rate of absorption of salts in the soil 

 solutions to water under the var\'ing condi- 

 tions of growth and transpiration. Never- 

 theless, information of this nature is im- 

 portant. 



In spite of all the recent work, the phys- 



