157 



Among the special forms of injury which can set in during long con- 

 tinued, intensive drought, especially in light soils, one especially deserving 

 more thorough discussion is 



The Effect of Drought Upon Germination. 



When the water scarcity occurs after the seed has passed the first 

 stages of germination, the results are less serious, if dry seed has been sown 

 on open ground than if seed previously soaked has been used. These dis- 

 advantages affect the development of the young individual in varying de- 

 grees dependent upon the kind of seed and the age of the seedlings when the 

 drought takes place. According to Will's repeated experiments'^ with seeds 

 of monocotyledons and dicotyledons, the seeds of the former seem in general 

 to be somewhat more resistent. The cereals without glumes (wheat and 

 rye) are very little sensitive to a period of drought, if it occurs during 

 germination. Barley and oats, however, are injured more easily, and the 

 horse-tooth maize has very little power of resistance. Saussure- found 

 that maize, beans, poppies and garden campion are very susceptible to 

 drought during germination. Nowoczek^ in his experiments repeatedly in- 

 terrupted the supply of water, until the power of germination of the seeds 

 was quite lost, and found that the seeds of grains resist the changing con- 

 ditions of moisture and drought better than rape, flax, clover and peas, 

 which lose their germinating power earlier, but even after a period of 

 drought these seeds can be revived. Experiments on the Gramineae showed 

 that after each drought period the fibrous roots, already formed, died, and 

 the outermost leaves dried up, but that, when water was again supplied, 

 new adventitious roots were formed from the first node (see Vol. I, p. 102) 

 and the last leaves developed further. This statement applies especially to 

 oats and to a greater or less extent to barley, wheat and maize. 



It should be considered as universally well-established that soaked and 

 then carefully dried seeds, when put again into water take it up more quickly 

 than do air dry, non-soaked seeds of the same size. Such seeds in fact 

 germinate a few days earlier. 



Tautphous* and Ehrhardt'^ made experiments giving results which 

 were expected at the start, — viz., that plants suffer so much the more, the 

 further germination has advanced; i.e., the more developed the plumule is 

 when the drought begins, the greater the damage. Will found the seed of 

 peas in part especially sensitive to drying out. The testa was broken by 

 many small cracks in most cases reaching into the inner layers. With re- 

 peated soaking, the palisade layer was broken into unequal pieces, the 



1 Will, Ueber den Einfluss des Einquellens und Wiederaustrocknens auf die 

 Entwicklung-sfahigkeit der Samen, sowie iiber den Gebrauchswert "ausgewach- 

 sener" Samen als Saatgut. Landwirtsch. Versurhsstationen XXVIII, Parts I and 2 

 (1882). 



2 Annales des sciences nat. Bot. 1S27. Janv. 



3 Ueber die Widerstandsfahlgkeit junger Keimlinge. Wissensch. prakt. Unter- 

 suchung-en etc. von F. Haberlandt, Vol. I, p. 122; cit. Biedermann's Centralbl. I, p. 

 344. 1876. 



4 Freiherr von Tautphous. Die Keimung- der Samen bei verschiedener Be- 

 schaffenheit derselben. Mtinchen 1876; cit. Bot. Jahresber. 1876, p. 882, 



5 Deutsche landw. Presse, Jahrg-. VIII, No. 76; cit. von Will, 



