56 



V. INFLUENCES OF LIGHT UPON THE 

 SPROUTING OF SEEDS. 



" On other occasions, from the want of tmie, the seeds, instead of being 

 allowed to germinate on damp sand, were sown on the opposite sides of pots, 

 and the fully grown plants measured. But this plan is less accurate, as the 

 seeds sometimes germinate more quickly on one side than on the other. It 

 was, however, necessary to act in this manner with some few species, ascer- 

 tain kinds of seeds will not germinate well when exposed to the light 



This occurred in the plainest manner with the seeds of Papaver vaguni and 

 Delphiniu'tn Consolida, and less plainly with those oi Adotiis astivalis and 

 Ononis minntissinia. Rarely more than one or two of the seeds of these 

 four species germinated on the bare sand, though left there for some weeks ; 

 but when these same seeds were placed on earth in pots, and covered with 

 a thin layer of sand, they germinated immediately in large numbers." — 

 Darwhi, Cross and Self Fertilization, Atner. ed. ij. 



Of late years there has been more or le.ss said concerning the 

 sowing of seeds for test upon the surface of .soil and covering with 

 gla.ss, in order that every seed ma}^ be watched, and certain seed 

 testing apparatuses have l^een devised upon this principle. It ap- 

 pears from Darwin's experience that with some seeds grave errors 

 may occur from this practice, and further evidence of the same 

 nattu'e is furnished from the tests here recorded. The .seeds, in 

 the following trials, were sown upon the surface of .soil in pots or 

 pans, the pots, tinless otherwi.se mentioned, being phniged in 

 sphagnum moss, to keep the soil moist. Over the top of the pot 

 or pan was placed a pane of gla.ss, or a close fitting iron saucer or 

 a board. 



40. Papaver Rhoeas, English Poppy. — Henderson. 



50 seeds on sand, in 4-inch pots plunged in sphagnum. 

 No. I, covered with glass. 



Epitome. — Sprouting was very much slower in the seeds ex- 

 posed to light, and total .sprotiting was 18 per cent, less in the 

 same case. 



