10 N. H. AGR. EXPERIMENT STATION. [Bulletin 198 



fact, crop plants are frequently classified according to the part of the plant 

 which is used commercially. 



In many cases all parts of a single plant are of economic value, while on the 

 other hand with certain other crops particular portions of the plants are of such 

 great commercial value that they are grown primarily for those specific parts. 

 Commercially the object to be obtained is the greatest profit, and a big factor 

 in increasing profit is the attainment of a maximum yield consistent with good 

 quality. Some of the parts of a plant such as the leaves, stems, roots, etc., 

 are more closely associated with vegetation, while others such as the fruits 

 (apple, pear, peach, etc.) and the grains, etc., the edible portion of which may 

 be a vegetative structure, are more or less closely associated with reproduction 

 and quite frequently with sexual reproduction. Inasmuch as it has been 

 shown quite definitely that all of our cultiu-al practices such as methods of 

 fertilizing, methods of pruning, methods of tillage, etc., affect materially the 

 type of growth, and, therefore, the yield of the respective portions of the 

 plants, it is important to know how these external factors affect plant meta- 

 bolism and bring about their respective results. 



Work upon the project has just been started. 



Relation of Light to Fruit Production. — This project was arranged co-opera- 

 tively with the Department of Horticulture, April, 1920, and represents a 

 part of the general problem of the Department of Horticulture deaUng with 

 the various factors affecting fruit bud formation. Numerous external factors 

 such as the amount of light, the amount and proportion of available mineral 

 nutrients, the moisture supply, the temperature, the manner of pruning, etc., 

 it is generally recognized, affect fruit bud formation and fruit production. All 

 of these external factors affect the internal conditions of the plant and it is 

 believed bring about their respective results by modifying conditions within 

 the plant. A better knowledge of conditions within the plant which are asso- 

 ciated with lack of fruit production, as well as those which are associated with 

 fruit production, should aid materially in solving the problem of determining 

 best commercial practices. 



The Station is fortunate in having two Yellow Transparent apple trees, which 

 bear at different times in alternate years. A large nuniber of samples have 

 been taken from these trees at different times of the year and are being 

 analyzed. 



Method for the Determination of Arsenic. — The Department is co-operating 

 with the Department of Botany upon the project entitled: "Studies on the 

 Effect of Fungicides and Insecticides upon Plants." In studying the relative 

 adhesiveness of insecticides a method for the determination of arsenic in the 

 presence of plant tissues is essential. The department has been working upon 

 this problem, and a promising method has been developed. 



Department of Entomology. 



Control of Root Maggots by Insecticides. — The insecticidal properties of to- 

 bacco dust and lime were the subject of the principal investigations in the De- 

 partment of Entomology during the summer of 1919. Encouraging progress 



