938 



SCIENCE. 



[X. S. Vol. XXI. Xo. 547. 



physics and chemistrj^ alone. Nor is it 

 possible to offer such explanations without 

 the assistance of these sciences. The prog- 

 ress of the work in physiology is indis- 

 solubly bound up in the development of 

 other sciences. The benefits are, however, 

 mutual, and as physiology acknowledges 

 the fundamental importance of these re- 

 lated sciences, they in turn must acknowl- 

 edge the important contributions, often of 

 fundamental nature, which have resulted 

 through physiological investigation. 



In such a paper it would be impossible 

 to do more than outline briefly some of the 

 relationships of special problems which, for 

 one reason or another, merit emphasis. In 

 general, the problems in plant physiology 

 have been well brought out and system- 

 atized through the monumental Avork re- 

 cently completed by Professor Pfeft'er. To 

 him the science owes a debt of gratitude 

 which may be acknowledged as well by one 

 Avho attempts to suggest future work as 

 by the historian. Again, due recognition 

 should be made of those who have in recent 

 years based upon this or any similar topic 

 valedictory addresses before various botan- 

 ical organizations — notably, those of Pro- 

 fessors Vines, Ward, Barnes, Reynolds 

 Green and others. 



The fact that every cell or organ re- 

 quires its food materials, or at lea.st its 

 nutrients, in liquid form, readily empha- 

 sizes the fundamental importance of those 

 problems suggested by the relation of the 

 plant to solutions. The mechanisms for 

 absorption and the general and special 

 diosmotic properties of the living cell, all 

 of which have been studied with the most 

 consummate skill, have yielded matchless 

 results ; yet the rewards for future research 

 show at present no distinct limitations. It 

 has not been possible to determine the 

 nature of the plasmatic membrane which 

 directly or indirectly possesses such marked 



powers of selection and accumulation. The 

 conditions under which the activities of 

 this membrane may be modified are but 

 poorly understood ; and it is, perhaps, quite 

 beyond the present possibilities to deter- 

 mine the mechanism of this modification, 

 for in that must be involved one of the 

 most important vital activities of proto- 

 plasm. Perhaps, when much more data 

 have been accumulated by a study of 

 l^lants of diverse habitat, the conditions of 

 this modification may be more clearly dis- 

 tinguished. It is known that continued 

 endosmosis of a particular solute depends 

 largely upon the use or transformation of 

 this solute within, yet it is not always pos- 

 sible to demonstrate any change in the 

 substance absorbed. In any event, it is 

 necessary to ask further light upon the 

 exosmotic resistance of the plasmatic mem- 

 brane to the accumulation of turgor-pro- 

 ducing substances, or, in other words, to a 

 further explanation of what may be 

 termed one way penetration. To these 

 phenomena the processes of excretion and 

 secretion are closely allied, whether they 

 are ultimately, periodically, or continu- 

 ously the function of certain protoplasts. 



Further chemical knowledge is needed 

 dealing with the meaning of high pressures 

 and of the accommodation of very high 

 pressures in the fungi. As a rule, those 

 protoplasts seem to be resistant to such 

 high pressures which are also resistant to 

 cold, desiccation and other stimulation. 

 IMayerburg, working under the instruction 

 of Professor Pfeffer, has recently applied 

 himself to a study of the method by means 

 of which the organism may regulate its 

 turgor. It is evident that one of two 

 propositions must be assiimed, and that 

 increased ti;rgor may be produced either 

 (1) by the penetration of substances from 

 without, or (2) by substances of strong 

 osmotic action produced within the cell 



