422 



had been damaged in threshing, even if the seed was left for sometime in 

 the acid. Frequently, treatment with sulfuric acid for half an hour will be 

 sufficient if the seeds have been thoroughly wet by stirring. When the 

 treatment is completed the acid should be thoroughly washed off with clean 

 water and then immediately with lime water for at least 5 to 20 minutes. 

 Microscopic investigations of seed treated in this way showed that (in 

 Acacia Lophanta) the sulfuric acid had removed not only the cuticle but 

 also the greater part of the palisade cells and had stopped before reaching 

 the "light line." Yet the seeds could swell in water only when the acid had 

 penetrated the light line in some places^ Therefore, this cell layer, present 

 in the seed shell of all the Leguminaceae, according to Mattirolo-, con- 

 sisting of an especially dense cellulose, prevents the seeds from rapid ab- 

 sorption and elimination of water. 



Connected with this innate hard-seeded condition is the hardening of the 

 seed membrane during germination. With those seeds which, in germi- 

 nation, pushed their cotyledons above the soil, the cap-like seed shell is 

 gradually pushed off, if it has been retained until the moisture is absorbed 

 and thus remains flexible. But if a hot, rainless period sets in suddenly, 

 the cap dries on the cotyledons, preventing their development, as well as the 

 breaking of the young stem. In case it is not destroyed, it is twisted to 

 one side. Lopriore^ mentions here the germination of beans. I have ob- 

 served similar phenomena in cucumbers, pumpkins, melons and the seeds of 

 stone fruits. The retention of the dry, stony shell shows itself most de- 

 structively in the seedlings of plums, peaches and other Amygdalaceae. 

 SprinkUng of the seed bed in the evening is, therefore, a precaution which 

 should not be omitted. 



1 Hiltner und Kinzel, tJber die Ursachen und die Beseitigung der Keimungs- 

 hemmungen bei verschiedenen praktisch wichtigeren Samenarten. Naturwissensch. 

 Zeitschr. f. L,and- u. Forstwirtschaft 1906, p. 199. 



-' La linea lucida nelle cellule malpighiane dcgli integumenti seminale. Torino 

 1885, cit. von Hiltner und Kinzel. 



3 Berichte d. Deutch. Bot. Ges. 1904, Part 5, p. 307. 



