84 



Bulletin 393 



TABLE 37. Set of Fruit on Spurs Inclosed in Opaque Bags and on 

 Spurs Inclosed in Translucent Bags 



on all inclosed flowers were green; those on exposed flowers had a reddish 

 tinge, even before the petals unfolded. The leaves on all the inclosed 

 spurs were smaller than those on the exposed spurs. At the time when 

 the fruit-setting spurs were counted, it was observed that there was a 

 tendency for fruit in the translucent sacks to attain the June-drop size 

 before it fell, whereas in the opaque sacks the fruit fell when very 

 small. All the flowers in the experiment were self-pollinated if polli- 

 nated at all. 



The figures indicate that exposure to sunlight is an added advantage 

 in fruit setting. The results agree with those of Lubimenko (1908), who 

 finds that illumination is essential during the early stages of development 

 of young fruit. 



Inclosing the spurs in bags inhibits the free circulation of air, and trans- 

 piration is probably reduced as a result. The air temperature in the 

 brown bags would be higher than that in the white bags on sunny days. 

 The diffused light in the translucent sacks would be sufficient for some 

 photosynthetic activity, while practically all light is excluded from the 

 opaque sacks. The leaves in the former, being exposed to light, would 

 probably have greater osmotic properties than those in the dark (Chand- 

 ler, 1 9 13). The advantage of having leaves with the greater osmotic 

 properties would be that more sap would tend to flow in the direction 

 of the spurs which produce such leaves. This sap would be available 

 for the setting of fruit. 



RELATION BETWEEN SEED FORMATION AND FRUIT DEVELOPMENT 



It is commonly supposed that the apples which are poorly fertilized 

 and which consequently develop few seeds, tend to fall off during the June 

 drop. That there is a close relation between seed formation and fruit 

 development is shown in the following paragraphs. 



198 



