From experiments in the same field, using definite amounts of nitrate of soda per plant, Work[7] concluded that while adequate carbohydrate supply is necessary for fruiting, excess carbohydrate did not, in itself, occasion unfruitfulness but was more likely to represent an accumulation of material unused by reason of deficiency in some other factor--often nitrogen. It was shown that nitrate of soda does not injure tomatoes until a concentration in the soil is attained which is strong enough to plasmolyze the cells, that is to withdraw water from them by osmosis. Nor were a wide variety of nitrogen and moisture and manure treatments sufficient to induce the Bonny Best variety to "run to vine." Some varieties are subject to this trouble, mostly of the large, late types. Murneek[8] has shown that the fruitfulness of a plant may greatly affect its internal condition, its vegetative performance and its later setting of fruit. A heavy load of developing fruit, with limited soil resources, tends to limit growth and setting. Removal of fruit induces renewal of vegetative growth and of fruit setting. Failure to set fruit favors vigorous vine growth. This failure may be traceable to various causes. (1) To damage to floral parts as the blasting of the pistil by heat and drouth. Flowers of some varieties show tendency toward elongation of pistils with subsequent failure to develop normal fruit. Smith and Howlett have shown that environmental conditions as well as heredity influence this elongation. (2) To injury by insects as thrips. (3) To the character of the variety used, the Bonny group being very slightly susceptible to failure from over feeding with nitrogen while some late sorts readily "run to vine." (4) Shortage of nutrient elements as nitrogen or phosphorus or others. (5) Lack of adequate light or short day. In such cases, there may be excess of nitrogen for current need with resultant over-development of leafage. Thus, excess vegetative growth may be a result as well as a cause of poor setting. Phosphorus Fertilizer experiments fairly generally point to the frequency with which phosphorus is the limiting factor among nutrients in tomato production. MacGillivray[9] has studied the phosphorus content of the various parts of the plant, concluding that this element is important throughout and not alone in seed making or in rapidly growing parts as has been believed. Hepler and Kraybill[10] found some years ago and others more recently have confirmed the influence of liberal phosphorus treatments upon earliness. [Illustration: FIGURE 5.--Effect of omission of phosphorus from complete fertilizer in Western New York.] Potash The potash requirement of the tomato has not been as thoroughly studied as the requirement for the other two major elements. It is thought that potash has a part in building up sugars into more complex carbohydrates.