52 CARNEGIE INSTITUTION OF WASHINGTON. 



earlier stages and increases progressively, so that the proportion of 

 solid material is highest and of water lowest at maturity. The stems 

 and leaves of succulents and such berry-like fruits as the tomato 

 {Ly coper sicum) have been found to reverse this relation, and melons 

 and similar structures probablj^ do the same. Some account of 

 the obvious features of the growth of the tomato was given in the 

 previous report, and a more detailed study has yielded some gener- 

 alizations of value both as to the course of growth and its funda- 

 mental physics. 



When we take up the facts disclosed by chemical analyses of 

 tomatoes, five things must be taken into account in any attempt to 

 make a physical-chemical explanation of growth, as follows: (1) the 

 proportion of sugar, including the mucilages, in the dry material 

 increases from 9 to 37 per cent in the stage of enlargement including 

 the formation of the seeds; (2) the acids, which include malic, phos- 

 phoric, and citric, increase toward maturity; (3) the albumins decrease 

 with development; (4) the ash or metallic bases increase from 4.5 to 

 10.75 per cent of the dry weight; and (5) the proportion of cellulose 

 lessens as the fruit proceeds toward maturity. 



The reduction of the auxographic measurements of the growth of 

 fruits and of the swelling of living and dried sections furnishes informa- 

 tion upon which the following conclusions may be based : 



1. The rate of increase in diameter of such globose, berry-like fruits 

 is not a correct or even approximate measure of actual growth con- 

 sidered as an accretion of water and solid material. 



2. The time at which the greatest increase in diameter takes place 

 may coincide with the greatest growth as exemplified in previously 

 described observations, but the increase in thickness is not a, direct 

 index of growth in such bodies. Actual growth varies as the cube of 

 the radius. 



3. The culmination of the rate may not be reached until the fruit is 

 in a stage approaching maturity. Then the maximum accretion 

 generally takes place in a stage subsequent to the highest rate of 

 increase of the diameter. 



4. The internal factors which determine the rate and amount of 

 growth of the tomato include the soluble sugars and the salts or bases 

 which increase toward maturity, as well as the albumins and celluloses, 

 which decrease with development, while the amino-acids, not deter- 

 mined, probably do not vary so widely as to affect their value as growth 

 accelerators. 



5. The conjunction of low acidity and low salt-content and sugar- 

 content would give a set of conditions for high imbibitional swelling of 

 a pentosan-protein plasma in the earlier stages of growth which would 

 be capable of carrying the fruit to an enlargement of 3,000 to 4,000 per 

 cent of the dry matter, as determined by previous experiments in the 



