46 Proceedings of Indiana Academy of Science 



(45) in plant cells within the temperature range ordinarily present, for 

 a rise of only 15° C. causes a pressure change from 100 to 105.5 (1, 

 Bd. I, p. 120) and this, to a degree, follows the laws of gaseous pres- 

 sure (46). Brown and Escombe have opened up an interesting field in 

 showing that the diffusion of CO- is not dependent on the size of the 

 leaf pores but is proportional to their diameter (47). In like manner 

 the diffusion of CO2 as first shown by Graham constitutes an interest- 

 ing topic. A study of diffusion in gelatine as investigated by Hiifner 

 and Hagenbach (43, Bd. I. p. 445) and compared to protoplasm would 

 be of value. Further studies are needed concei-ning the behavior of 

 certain cell walls to the diffusion of liquids and gases. Conduction of 

 food materials takes place rapidly in some parts, but is prevented en- 

 tirely by girdling. The length of life, however, of that part of a tree 

 above the girdle varies. 



Many problems remain concerning the storage of food. Trees for 

 example, are distinguished from annuals because the latter store their 

 resei*ves permanently only in the seeds, and they differ from perennials 

 because the latter store their reserves subterraneanly (48, p. 225). Many 

 problems arise concerning the nitrogen question, particularly regard- 

 ing autotrophic plants. There is the question of nitrites and nitrates 

 and especially a question of nitrites in developing green plants. Ques- 

 tions arise concerning vegetable proteids and their synthesis, under 

 '"«;rtain conditions and points relating to sulphur. Plants of Chenopo- 

 dium vidvaria and flowers of Crataegus oxyacantha evolve a nitrogenous 

 compound in .such quantity that a glass rod dipped in hydrochloric acid 

 emits fumes when brought under a bell jar with such specimens. Wicke 

 says this substance is trimethylamine in Chenopodium (49). The nitrogen 

 problem is one requiring investigation by both physiologist and chemist. 



Ethereal oils constitute a question. In Dictamnns albus the oil 

 may vaporize to such an extent as to ignite when a flame is brought 

 near it and hence many such flowers may be more fragrant at night 

 (1, Bd. I, p. 502). In the daytime, however, the change in the 

 diathermanicity of the air which would assist in reducing the heat of 

 the sun's rays would be slight notwithstanding the efficiency of these 

 vapors in that respect as mentioned above (50 and I, Bd. II, p. 848). 

 Green and other colored leaves can absorb 50 to 90 per cent of the 

 sun's energy (50). Certain species of Citrus possess highly inflammable 

 oil. Among cryptogams the oily nature of certain parts is well known. 

 In Lycopodium the spores flash into a beautiful array of scintillations 

 on ignition, hence their frequent use in pyrotechnical displays. 



Oligodynamic studies will bear further incjuiry. Grafe has made 

 valuable studies on cell chemistry and Haas and Hill have recently 

 mentioned various metabolic problems (51). Electro-culture and the 

 physiology of seedlings are worth-while problems. In 1878 Sachs stated 

 that an electric current passed from the stigma to the ovary pedicel 

 of Berberis stimulated all the stamens, but when sent in the reverse 

 direction no stimulation was produced (14, p. 685). Other stimuli 

 produce comparable results, for when plants are passed from dark to 

 light and vice versa the stimulation is different (1, Bd. II, p. 504). 



