282 University of Calif ornia Publications in Botany [Vol. 5 



of the F^ hybrids is thus particularly characterized by the early falling 

 of their flowers, and we attempted first to inhibit flower-fall in the 

 expectation that such inhibition might be accompanied by the pro- 

 duction of a greater proportion of normally matured ovules and 

 pollen grains. It is, however, obvious that we might have suc- 

 ceeded in bringing about an induced parthenocarpy in which the 

 Fj hybrids would have held their flowers after anthesis irrespective 

 of the production of normal pollen and ovules and the accompanying 

 pollination and fertilizations. Particular emphasis also was laid 

 upon eliminating flower and fruit-fall since the subject is of special 

 importance in many species cultivated commercially. AVith particular 

 reference to the nutrition factor in this connection it appears to have 

 become almost a dictum by gardeners that the tomato will drop its 

 flowers and young fruits when grown in soil over-rich in barnyard 

 manure, while many orchard fruits fall at different periods of devel- 

 opment Avithout specific cause so far as determined. The problem of 

 flower and fruit-fall has not. so far as we have been able to discover, 

 been investigated from the strictly physiological point of view, the 

 only type of investigation that would seem to promise valuable results. 

 We have, in particular, been unable to find notice of experiments 

 similar to ours in which an effort was made to eliminate flower-fall 

 by varying the total and relative concentration of the available mineral 

 nutrients (cf. Lloyd, 1914). 



These experiments have extended over some three years. During 

 the first two years interest centered upon the eff'ect of the individual 

 mineral nutrients, while by the experiments of this last year the effect 

 of varying the total concentration of nutrient salts was sought. Rooted 

 cuttings FjHSS were employed during the first year and thereafter 

 seedlings of the same hybrid a month old or less. The plants, in six- 

 inch pots, heavily paraffined, were grown to maturity under glass. The 

 temperature about the plants was rather highly variable but moisture 

 conditions were maintained fairly constant. 



Table 3 has to do with the experiments of the second year. Forty- 

 eight seedlings were planted in pots each of which contained 1720 g. 

 of washed sand. The plants were divided into three groups which 

 are mentioned in table 3 as groups A. B. and C. Each group con- 

 sisted of eight plants, with a duplicate for each of the eight which 

 received identical treatment in each case. In group A of table 3 

 nitrogen was the only varying factor and the other salts remained 

 constant in amount within the group. Similarly in group B phos- 



