296 



drought occurs, than if it had been sown naturally. Zawodny^ has proved 

 this experimentally for cucumbers. In this connection reference must be 

 made to the already discussed interruption of germination by drought. 



Droppixc of the Fruit. 



Besides the dropping of pears already mentioned, which Miiller-Thur- 

 gau observed as the result of drought at the time of blossoming, fruit-bearing 

 trees have an annual house cleaning during which poorly nourished blossoms 

 or young fruits are dropped. The flowers developing last at the tips of the 

 inflorescences, especially those at the ends of branches, are the ones cast off. 

 There is not enough plastic nutriment at hand for development. The fruits 

 nearest to the source of supply, the trunk axis, take up the nutritive sub- 

 stances at the expense of the organs further out. For fruits cultivated on 

 trellises, these nutritive relations can be regulated artificially, since a large 

 part of the unfavorably placed specimens can be removed with shears soon 

 after the fruit is set. 



In growing fruit for market very exact consideration must be given the 

 moisture requirement, especially that of peaches and apricots. When the 

 stone begins to harden, the most water is needed, and the dropping is often 

 caused by a single dry period. Before and after this stage of development, 

 however, more care must be used in watering, since otherwise sprouts are 

 produced tOo early, which divert the material necessary for the maturing of 

 the fruit. Then, at a later stage, the fruit will drop from a lack of nutri- 

 ment, or, at least, be injured by it. 



We have already mentioned in previous chapters that mature fruits 

 may drop because of a late dry period, and it is now necessary to recall that 

 fruit, injured by a late spring frost, is sometimes found in great quantity 

 on the ground. All causes which lead to the sudden lost of function of an 

 organ ultimately efifcct its dropping. 



The Drying of the Inflorescences on Decorative Plants. 



This phenomenon is often met with especially by amateur growers of 

 potted plants. Aside from the effect of dry air which will be treated later, 

 and the dryness of the soil already mentioned, there are two circumstances 

 that come under consideration here. Both represent a starving of the blos- 

 som buds. In one case it is actually a lack of nitrogen which manifests it- 

 self when the plants stay in the pots too long, in the other case it is a lack 

 of food for the blossoming organs, since other organs have taken it. 



Our azaleas and camellias serve as the most usual example of the latter 

 case. Plant lovers complain very frequently that the plants which have a 

 great many buds do not open their buds in the house. In azaleas the buds 

 become dry, in camellias they fall. In both cases fresh, rapidly and vigor- 

 ously growing shoots develop prematurely directly under the blossom buds. 



1 Zawodny, J., Keimung- der Znaimer Gurke. Cit. Bot. Jahresber. 1901. Part II, 

 p. 236. 



