794 



SCIENCE 



[N. S. Vol. XXXVII. No. 960 



to have used one of these tests or to have pur- 

 sued an equivalent course in plant physiology. 



Correlated with the objection just noted is 

 another concerned mainly with the teaching 

 of the restricted usage in courses in elemen- 

 tary botany in secondary schools. The clear- 

 est approach in beginning a course in botany 

 in a high school lies in leading the pupil to 

 think of plants as separate living things, each 

 of which is an individual, which has, like an 

 animal, its problems of food getting, nourish- 

 ment, protection, etc. The university concept 

 of the word food, however, requires that the 

 pupil think of a green plant as an aggregate 

 of different kinds of cells which bears a very 

 different relation to its surroundings as re- 

 gards its food than the living things, i. e., 

 animals, with which the pupil is familiar. The 

 pupil thus loses the definiteness of the idea of 

 a green plant as an individual with problems 

 like those of animals, and has to think of it 

 as something which does not get its food from 

 without, but must manufacture it within its 

 cells. The phraseology of this usage of the 

 word food has been written into the elemen- 

 tary texts without, so far as I have been able 

 to find, any attempt to make the pupil under- 

 stand how or why it differs from the older 

 usage. As a consequence he learns to use the 

 word food, in the class at least, in a very dif- 

 ferent way from his ordinary understanding 

 of it, but usually without any realization of 

 the inconsistency. 



Complications follow the restriction in 

 meaning which do not appear to have been 

 realized. In the case of green plants food, in 

 the restricted sense, includes only organic 

 material prepared within the cells of the plant 

 and available for assimilation by any of the 

 cells. In the case of animals, food is first, 

 the organic material which, if taken into the 

 alimentary tract, is able to be digested, and 

 second, the material resulting from such di- 

 gestion, even yet estra-cellular, but comparable 

 with the material recognized as " food " of 

 green plants. Thus it appears that future 

 dictionaries will need to give at least two defi- 

 nitions of the word food. 



If we accept the modified definition of food 



as desirable, we shall then have to face the 

 task of making it part of the common knowl- 

 edge of all who use the English language. 

 Under present conditions it is practicable to 

 teach it only to the minute proportion who 

 pursue courses in plant physiology in colleges. 



Referring to the antithesis in thought to 

 which Barnes objected, it may be noted that 

 this has apparently given little or no trouble 

 to a number of well-known botanists who have 

 discussed plant nutrition in text-books. It 

 appears to have occasioned no difficulty in the 

 elementary texts of Atkinson and McDougal; 

 in the general texts of Bessey, Sachs, Stras- 

 burger, etc.; in the physiological treatise of 

 Jost. Ganong in his test-book of physiology 

 refers to the restricted meaning as desirable 

 but as probably impossible to promulgate. 



It seems to the writer as entirely unneces- 

 sary to attempt to make so great a distinction 

 between the food material of the individual 

 green plant as a whole and the food material 

 of its constituent cells, or between the crude 

 food materials of green plants and animals. 

 It is possible sufficiently to differentiate the 

 materials and their processes of preparation 

 without revising out of conscience the ordi- 

 nary meaning of an old and useful word. It 

 would appear sufficient to satisfy all the needs 

 of discrimination to use expressions like 

 " crude food " and " cell food." [Since the 

 preceding sentence was written, practically 

 the usage suggested there has been used in high 

 school classes with good results. The use of 

 the espression " cell food " emphasizes to 

 pupils the idea of the cells as the unit of struc- 

 ture and function in living things.] 



Finally it may be noted that in the last 

 analysis, it is strictly impossible to restrict 

 the word food wholly to organic material. 

 Barnes limited his discussion of the question 

 to carbon dioside and water and the carbon 

 compounds resulting therefrom. He expressly 

 escludes mineral salts from his consideration 

 as too small in amount to deserve attention. 

 Logically, however, they can not be escluded 

 even on this basis and especially not in view 

 of the fact that the nitrogen, sulphur and 

 phosphorus of protoplasm are derived from 



