636 SUMMARY OF CURRENT RESEARCHES RELATING TO 



BOTANY. 



GENERAL, 

 Including the Anatomy and Physiology of Seed Plants. 



Cytology, 

 Including- Cell-Contents. 



Structure of Protoplasm.* — W. W. Lepeschkin contributes a pre- 

 liminary paper dealing with work on the structure of protoplasm. The 

 author believes that living protoplasm is to be regarded as a colloidal 

 solution of the nature of an emulsion, which under certain conditions is 

 visible under the Microscope, and may be transformed into a gelatinous 

 foam with fluid, honeycomb-like walls. The writer is of the opinion 

 that such a structure is the only one which would account for the 

 physical and physiological characters of protoplasm. The colloidal 

 parts, which show " Brownian " movement in the plasma of the proto- 

 plasm, probably consist of various and heterogeneous chemical compounds. 

 Since the distribution of colloidal parts takes place very slowly, molecules 

 of chemical compounds arising in any particular part of the protoplasm 

 cause alterations in the protoplasm at that point, and bring about such 

 phenomena as prolongations of the cell, separation of special substances, 

 changes in the protoplasm, etc., which in their turn cause movements in 

 the plasma. Such a structure would explain the organization of the 

 protoplasm whereby reactions or conditions occurring in one part are 

 conducted to all other parts. If by the action of electricity, poisons, 

 etc., this colloidal structure is destroyed and coagulation ensues, then 

 life is destroyed. The contents of the protoplasm, i.e. nucleus, 

 chromatophores, etc., all appear to partake of this colloidal nature. The 

 author believes that all phenomena exhibited by protoplasm may be 

 explained by this " living plasma " theory. 



Chemical Composition of the Plasma-membrane. f — W. W. 

 Lepeschkin has studied the chemical composition of the plasma- 

 membrane, i.e. the plasma-layers which form on the surface of proto- 

 plasm and possess selective osmotic properties. Numerous experiments 

 lead the author to believe that the power of diffusion is due to the same 

 causes which render possible the diffusion of salts, acids, and other 

 readily soluble substances, i.e. to dissolved molecular water in the 

 dispersion-medium. Albuminoids or closely allied compounds also play 

 an important part in dispersion, likewise lipoids and oily substances, 

 although it is still doubtful whether the latter are simple or combined 

 with a mixture of lecithin and cholesterin. At present it appears as 

 though all the above substances exist in the dispersion-medium either in 

 a molecular solution or as a loosely combined chemical compound ; the 



* Ber. Deutsch. Bot. Gesell., xxix. (1911) pp. 181-90. 

 t Ber. Deutsch. Bot. Gesell., xxix. (1911) pp. 247-61. 



