372 



SCIENCE. 



[N. S. Vol. VII. No. 16a 



tlie chemical activities of the cell is possi- 

 ble. The very apparent interprotoplastic 

 threads have so far received no conclusive 

 interpretation. Protoplasmic substance it- 

 self may wander from cell to cell, water, 

 nutritive material, irritable or regulatory 

 impulses may traverse these convenient 

 pathways, but so far it has not been demon- 

 strated that the structure in question is 

 necessary for any of these functions. 



The oldest branch of the subject is that 

 of nutrition, and the beginnings of chem- 

 istry were made in researches upon the re- 

 lation of the plant to the soil and air. The 

 necessity and method of absorption of min- 

 eral salts and carbon dioxide is fairly un- 

 derstood, but the specific uses of the for- 

 mer and the manipulation of both classes 

 of substances within the plant is unknown. 

 Thus, for instance, the formation of food in 

 the leaf from carbon dioxide and water is 

 regarded as a photosynthesis, yet nothing 

 is known of the process except that at an 

 advanced stage a complex carbohydrate is 

 produced. It is quite within the range of 

 possibilities that the same products may re- 

 sult from a photosynthetic action on other 

 carbon compounds. The composition of 

 chlorophyll and its relation to the chloro- 

 plast are still in question. It may be 

 lodged in interstices of the living matter or 

 may form organic union with it. The 

 chlorophyll may act as a converter of light 

 into energy made available to the chloro- 

 plast, or its molecules may act as carriers 

 in the synthesis. It is becoming even more 

 open to doubt as to whether the activity of 

 chlorophyll is exactly coincident with its 

 absorption bands. Investigation in several 

 lines must cooperate to solve this problem. 

 The chemosynthetic activity of the nitrobac- 

 teria, and the thermosynthetic and electro- 

 synthetic processes of other organisms, are 

 hardly so well known. 



The acquisition of nitrogen is a much 

 vexed question, and the dawn of new in- 



vestigations threatens to upset long cher^ 

 ished ideas as to the relation of the ' auto- 

 phytes ' to organic substances. The use, 

 formation into crystals, resolution and 

 transference of mineral substances in the 

 plant body, is not satisfactorily explained. 

 The balance and combined action of the 

 several mineral elements in the soil is a 

 matter of which we have no definite com- 

 prehension. Are the salts presented to the 

 plant in commercial fertilizers absorbed as 

 such and used as food, or are they sub- 

 jected to synthetic activities, similar ta 

 those of the chlorophyll apparatus ? Thus 

 the presence of sodium salts in the soil is a 

 benefit, amounting to a necessity in some 

 instances, although this abundant element 

 does not actually enter into the composi- 

 tion of protoplasm or plastic substance. 

 The translocation, storage and formative 

 selection of reserve material is bound up 

 with that of fermentation, and the physiolo- 

 gist has progressed so far as to know that 

 the preparation of reserve material, fluid 

 and solid, for transportation is accom- 

 plished by means of ferments. He has 

 isolated a few of these enzymes and has 

 come to know that scores of others exist 

 with action and chemical constitution un- 

 identified. The vitalistic theory of fer- 

 mentation will doubtless lurk among the 

 residua of unexplained enzymic activities 

 for many years to come. Indeed, the recent 

 failure to extract a ferment from yeast 

 gives the hypothesis a new lease of life. No 

 doubt can exist, however, that the vital or 

 regulatory action of the organism does play 

 a part in these phenomena which we are 

 not prepared to appreciate, and the secre- 

 tory action concerned here and elsewhere 

 in the plant has not received a fraction of 

 the attention given such functions in ani- 

 mals. 



The paucity of information of the physio- 

 logist concerning the alkaloids, glucosides, 

 pigments and other compounds in the plant 



