FELIX G. GUSTAFSON 353 



solution. Mitchell et al. (17) have used carbowax in a concentration of 

 0.5 per cent with good results. Concentrations of growth substances 

 have ranged from a few parts per million to 300 ppm., but part of 

 this difference in concentration has been due to the type of chemical 

 used. Wittwer (26) has found that 25 to 30 ppm. of p-chlorphenoxy- 

 acetic acid gave satisfactory results. Not only has it been found that 

 hormone spray increases the setting of tomatoes in the greenhouse during 

 the winter, but it has also been found that if the first two or three 

 clusters of flower buds on plants grown outdoors in early spring are 

 sprayed the setting will be much increased. The cold of the early spring is 

 extremely unfavorable for tomato setting, perhaps because of poor 

 pollen development, but the pistils are perfectly capable of developing 

 into fruits if stimulated by growth-promoting substances. The chemicals 

 used to increase fruit-setting in the tomato are numerous, but the ones 

 most commonly used are indolebutyric, naphthaleneacetic, and naph- 

 thoxyacetic acids as well as several derivatives of phenylacetic acid as 

 p-chlorphenoxyacetic, 2,4-dichlorphenoxyacetic, and 2,4,5-trichlor- 

 phenoxyacetic acids. In passing it should be stated that in spraying 

 tomato buds or flowers either in the greenhouse or in the field the 

 resulting fruits are not always parthenocarpic since sometimes pollination 

 may have taken place before the spraying, but this pollination may be 

 so light that without the additional hormone the pistil would not develop 

 into a fruit. 



Recently two papers appeared adding another economic plant that 

 profits by hormone spray. Blondeau and Crane (i) and Stewart and 

 Condit (21) have reported that Calimyrna figs, which are usually pro- 

 duced only as a result of pollination by the fig wasp, produced partheno- 

 carpic fruits of normal size and color when sprayed with 2,4-dichlor- 

 phenoxyacetic, 2,4,5-trichlorphenoxyacetic, or indolebutyric acids. 

 These authors state that if the spray method proves to be adaptable to 

 commercial groves it will be of inestimable value to the California 

 fruitgrowers, as there will be no further need of growing the pollen- 

 producing caprifig trees. 



Figuies I to 5 illustrate typical parthenocarpic fruits produced by the 

 writer. Figure i of the John Baer tomato shows that externally there 

 is no difference between the seeded and seedless fruits; and in Figure 

 2 it is seen that internally the parthenocarpic fruit is like the normal 

 fruit in that it is fleshy, possesses prominent locules, but the ovules have 



