DEPARTMENT OF BOTANICAL RESEARCH. 53 



hydration of such colloids. Otherwise expressed, imbibition would be 

 capable of making a colloidal body like a fruit which would consist of 

 97.5 per cent water and 2.5 per cent solid matter. 



6. The higher salt-content and acidity of older fruits would operate 

 to lessen imbibition in the fruits, which in this stage would be high in 

 carbohydrates. 



7. The above facts support the conclusion that the distentive force 

 in growth of young fruits is chiefly imbibition. Osmotic action may 

 play the more important part in later stages. 



8. The growth of a fruit, therefore, is a resultant of two groups of 

 activities, one ordinarily classed as imbibitional and the other associated 

 with osmosis and turgidity. 



9. Young fruits include 1 to 4 per cent more solid material than 

 mature ones, these bodies being representative of a type of plant 

 structure in w^hich the dry w^eight does not increase with age. 



10. The amino-acids induce a greater swelling or absorption of water 

 by the cell-masses of growing tomato fruits than takes place in weak 

 acid solutions or in water. This fact is in agreement with, and is 

 probably fundamental to, the accelerating effect of these substances on 

 growth. 



11. Continuous measurements of tomato fruits reveal slackened 

 growth or shrinkage in the midday period corresponding to the time 

 of greatest transpiration, and it is concluded that water absorption 

 during this period is balanced by the loss from the surface, in accord- 

 ance with the behavior of many other structures, such as trunks and 

 twigs of trees, stems of sunflowers, joints of Opuntia, and leaves of 

 Mesemhryanthemum . 



Components and Colloidal Behavior of Plant Protoplasm, hij D. T. MacDougal 



and H. A. Spoehr. 



The principal conclusions established by our previously described 

 investigations which are of direct interest with relation to new results 

 to be presented are as follows : 



1. The protoplasmic mass of the active cell of the plant is a mixture 

 of carbohydrates, chiefly in the form of pentosans and albuminous 

 substances, with a probable very low but undetermined proportion of 

 lipins. In addition to the mucilaginous substances of the first, freely 

 soluble sugars may be present in the cell solutions. 



2. The principal components of plasmatic masses, the mucilages and 

 the proteins, are mutually non-interdiffusible, and hence when brought 

 together in the cell by minute accretions or mixed in liquid form must 

 be taken to form com.plex emulsions or mesh-works and to occur 

 separately both in disperse phase and disperse medium. 



3. Of the components of such a mass, the one that could be regarded 

 as the more sohd, as having the lesser attraction for molecules of water, 



