Septembeb 18, 1914] 



SCIENCE 



403 



nitrogen. Transpiration receives more careful 

 study because it is of importance in a number 

 of aspects. Without water in which plants 

 can absorb it, mineral food is as useless in the 

 soil as it is in a warehouse. Mineral food is 

 studied in water culture, in pot culture, and 

 in beds on the farm. In water culture, the 

 work is made as exact as it possibly can be, 

 using chemically pure salts, distilled water, 

 and the most insoluble containers. In the 

 field the work is made as practical as it can be, 

 using ordinary garden crops on ordinary farm 

 soil, with the fertilizers which are regarded as 

 generally available. As a matter of interest, 

 manure, ashes and commercial fertilizers used 

 in this experiment are analyzed on the 

 grounds, and the results of the analysis given 

 to the students. But the experiment is in- 

 tended and understood to show the students 

 what results they can obtain at home by meth- 

 ods of procedure which are practicable there. 

 Work on such a scale as these fertilizer ex- 

 periments must be done by groups instead of 

 by individual students, else the course will de- 

 mand more time than can be found in a single 

 year. 



Other phases of plant physiology receive less 

 attention. There are a reasonable number of 

 experiments on photosynthesis. But, impor- 

 tant as it is, this phase of plant activity is 

 relatively not subject to direct human control ; 

 a thorough familiarity with it is accordingly of 

 much less practical utility. The study of res- 

 piration is still briefer. Such subjects as geo- 

 tropism, and the others sometimes grouped 

 under the head of "Irritability," are treated 

 briefly in lectures, and passed over with an 

 easy experiment or two, not requiring more 

 than a day each in the laboratory. 



Practically in the place of this, the student 

 in the American college of agriculture is 

 taught chemistry. Chemistry is of course a 

 necessary part of agricultural education. Our 

 students study it for two years. But the plant 

 physiology and not the chemistry is the basis 

 on which their agriculture rests. 



The difference in the scientific foundation 

 makes the instruction in plant industry itself 

 different. Our courses in agronomy are full of 



plant physiology. In these cases, the special 

 plant physiology of the particular crops has 

 thorough study. Thus, the students of the 

 coconut measure the growth of leaf, root, 

 flowering branch and fruit. The growth of 

 the leaf is the easiest index to the general ac- 

 tivity of the tree, and accordingly receives 

 most attention. This work has now been car- 

 ried on so long, and such a mass of data has 

 been accumulated that it is possible to estab- 

 lish a figure which represents satisfactory ac- 

 tivity, and to determine approximately how 

 much this varies with the change in weather 

 from day to day. With this information, the 

 student can go into a coconut plantation and 

 determine with a high measure of probability 

 the average production from the grove two 

 years and a half hence; and he can do this 

 after 24 hours' observation. The estimate he 

 makes is a very much more reliable one than 

 can be made from a three months' study of the 

 present rate of production. We expect to es- 

 tablish standards of this kind for all of our 

 principal crops. But to do so, and get figures 

 which can be relied upon, is no small task. On 

 the coconut we have more than 100,000 single 

 measurements of rate of growth. Standards 

 of this kind are certainly worth having. I do 

 not think it admits of question that the abil- 

 ity to use, and if need be to make them, is a 

 valuable part of a student's education. 



The student also measures the absorption 

 of water by the roots of the coconut and its 

 transpiration from the leaves, and the absorp- 

 tion of mineral food by the roots. He learns 

 how much water the plant needs, and how it 

 responds to differences in the water supply. 

 When he gets done, he knows enough about 

 the physiology of the coconut to realize that 

 soil analysis, or even the decidedly more use- 

 ful analysis of the parts of the plant, will not, 

 by itself, give him any idea of whether or not 

 it is worth while to apply fertilizers. He 

 knows that if his trees are getting less mineral 

 food than they shoiild, it may be impossible to 

 remedy the deficiency by buying fertilizers, 

 and that the difficulty frequently can be 

 remedied, and remedied more cheaply, by the 

 use of water. In short, he understands the 



