i6o 



To the statement made heretofore that the seed of Acer retains its 

 germinating power until the following spring, the qualifying 'statement must 

 be added, that maple seeds of the Campestre group (Acer ohtusatum, A. 

 italutn, etc.), as a rule, germinate only in the second year. Only occasional 

 seedlings may be found after the first year. In many botanical gardens, how- 

 ever, trees of the Campestre series are said to furnish seeds usually germinat- 

 ing early. The explanation of this is that in seeding in such places, the first 

 seedlings are used for propagation. From this it may be concluded that the 

 peculiarity of producing seeds, which germinate promptly, may be made 

 constant by selection. This point of growing the earliest germinated seed- 

 lings separately as seed bearers, when making large seedlings, might be 

 recommended for the consideration of plant breeders. 



Blasting in Grains and Legumes. 



Under these circumstances the seeds do not mature since the plants 

 do not have enough water. Such a condition of great drought is most often 

 found on soils of a very porous structure where evaporation is very great 

 and the capillary movement of water from the subsoil is slight. 



Yet great scarcity of water will not always produce a blasting of the 

 blossoms. This depends essentially, as Hellriegel's experiments with grains 

 show, on the development of the plant when the water scarcity makes itself 

 felt. If, following the experiments\ a grain plant has had only a scanty 

 amount of water at its disposal, beginning at the time of its germination, 

 it reaches maturity in a period of the same length, or perhaps somewhat 

 longer, yet the whole growth is weak. The proportion of the harvested 

 grains to the dry substance, however, is always normal ; i.e., approximately 

 half of the dry substance is harvested in the form of grain. As in all 

 vegetative conditions, there is here also a minimum; if the water supply is 

 kept below this, no product worth naming takes place. 



If great scarcity of water occurs immediately after germination begins, 

 the grains remain alive for a long time (in the experiment up to six weeks) 

 and later develop vigorously, when the water is supplied in abundance. A 

 period of drought appears to be still less injurious if the grains are still in 

 the milk stage, i. e., have reached their normal size, but have not 

 finished their inner development and become hard. The work of the plant, 

 which now forms no new dry substance, consists in transposing the sub- 

 stances produced in the leaves to the storage organs, the seeds. 



In all periods of growtli between sowing and ripening, a longer scarcity 

 of water acts more injuriously the younger the plant is at the beginning of 

 the drought. AMien the long drought sets in while the seeds are sprouting 

 vigorously, the setback resulting therefrom cannot be overcome. The results 

 of continued drought are the more severe, the more water the plant has had 

 in its youth. If a plant has grown luxuriantly with abundant soil, up to the 



1 Hellriegel, Beitrage zu den naturwissensehaftl. Grundlugen des Ackerbaues. 

 Braunschweig. Vieweg 1883, pp. 589 to 620. 



