1019] HORTICULTURE. 41 



prises <iin> of ;i series of studies conducted by the senior author and othors at 

 the station to determine the factors involved In fruit setting among pomaceous 

 trees (B. 8. R., 38, p. 12). The work was carried on at the University of Chi- 

 cago in partial fulfillment of doctorate requirements. The tomato was selected 

 for study because of the nonavailability of fruit trees and because In its 

 general responses in vegetation and fruit setting it aeeords very closely to th< 

 observed in apple and pear trees. Several series of pot experiments were 

 started at different periods during the year. Various parts of the plants were 

 analyzed and studied with reference to variations in content of moisture, dry 

 matter, total nitrogen, nitrate nitrogen, free-redueing substances, sucrose, and 

 Starch, as well :is to related changes in plant structure and plant functioning. 

 The results are presented in a series of tables and diagrams and fully discussed. 

 Some related work of other investigators is briefly reviewed and a bibliography 

 of literature cited Is appended. 



The authors found that four general conditions existed in the relation of 

 nitrates, carbohydrates, and moisture within the plant itself and the responses 

 apparently correlated therewith. These are as follows: "(1) Though there be 

 present an abundance of moisture and mineral nutrients, including nitrates. 

 yet without an available carbohydrate supply vegetation is weakened and the 

 plants are nonfruitful. (2) An abundance of moisture and mineral nutrients, 

 especially nitrates, coupled with an available carbohydrate supply, makes for 

 increased vegetation, barrenness, and sterility. (3) A relative decrease of 

 nitrates in proportion to the carbohydrates makes for an accumulation of the 

 latter, and also for fruitfulness, fertility, and lessened vegetation. (4) A fur- 

 ther reduction of nitrates without inhibiting a possible increase of carbohydrates 

 makes for a suppression both of vegetation and fruitfulness." 



Whatever the conditions under which a plant has been grown, increased to^al 

 nitrogen and more particularly increased nitrate nitrogen are associated with 

 increased moisture and decreased free-reducing substances, sucrose, polysac- 

 Charids, and total dry matter. " Microchemical tests indicate very little differ- 

 ence in potassium content of individual cells whatever the condition of the plant. 

 Withholding moisture from plants grown under conditions of relative abundance 

 of available nitrogen results in much the same condition of fruitfulness and 

 carbohydrate storage as the limiting of the supply of available nitrogen itself." 



" In general, within the plant itself, in the stem from the top to bottom, there 

 is a descending gradient of total nitrogen and moisture, and an ascending grad- 

 ient in total dry matter, polysaccharlds, and sucrose. The proportion of free- 

 reducing substances to other carbohydrates, total nitrogen, and nitrate nitrogen 

 is variable. The great variations in the amount of carbohydrates in plants 

 grown under different nutrient conditions and in different parts of the same 

 plant indicate that in studying problems concerned with plant metabolism it Is 

 necessary to know the specific environment of the plant as a whole and of its 

 several parts." 



Fruitfulness was found to be associated neither with highest nitrates nor 

 highest carbohydrates but with a condition of balance between them. "The 

 conditions for the initiation of floral primordia and even blooming are probably 

 different from those accompanying fruit setting. The greatest number of 

 flowers are produced neither by conditions favoring highest vegetation nor by 

 conditions markedly suppressing vegetation. Lack of fruit development is not 

 alone due to the lack of pollination or fertilization. The flowers may fall so,>n 

 after pollination (markedly vegetative plants) or remain attached for many 

 days without development of the fruit (markedly nonvegetative plants)." 



The following deductions dealing with the nitrate, carbohydrate, and mois- 

 ture relations of the plant and various cultural practices were made: "Parts 



