192 Alfred J. Eivart: 



in the deeper layers the only seeds found are likely to be hard 

 macrobiotic ones. In fact, all the seeds found in the soil below 

 the surface needed treatment with sulphuric acid to produce 

 swelling and germination. Once they are swollen, the seeds are 

 incapable of remaining long living in a latent condition without 

 germinating, and this applies generally to the seeds of Legu- 

 minosae, whether cuticularized or not. 



Conditions for Germinatinn. — In addition to the usual state- 

 ment that water, oxygen, and a certain temperature are needed, 

 the proviso is required that the water and oxygen must be able 

 to penetrate the seed in sufficient quantity. Even when a seed 

 has absorbed water and swollen, it may remain dormant for a 

 long time without dying if the supply of oxysren is deficient or 

 the temperature low. Nobbe' and others have shown that the 

 moist seeds of Cirsium arvense, Papaver Rhoeas, Cherry, Oak, 

 etc., may remaiin alive without germinating for a year or more in 

 the soil. Fischer'^ states that the same is the case with many 

 water plants whose seed may remain germinable under water for 

 years, though fully soaked. He finds that the seeds of Sagittaria 

 xiKjittifolia, S. lAati/phylht, Sjuirf/aniiini ramosntn, S. simplex, 

 Alixnia Plantago, Fotaiiuiycton )i(it(ius, lucens and peetinatus, 

 Hipjjuris vuh/aris, Folygnnum amphihinm,- Scirpus loctistris 

 and niaritimus germinate little, or not at all, in pure water, but 

 readily if the water is allowed to foul and become sour, or if the 

 seieds are acted upon bv dilute acid or alkali (H and HO ions), 

 especially at high temperatures. Thus after 2 hours in 0.3 mol. 

 solution of ajcid at 40 deg. C, 75 per cent, germinated, whereas 

 after 2 hours at 4-6 deg. C. only 3.4 per cect. germinated at 

 the same subsiequent temperature (25-27 deg. C). Fischer con- 

 siders that as the seed coat is permeable to water, salts and acid, 

 the action must be a stimulating one exercised on the protoplasm 

 of the seed by the hydrogen and hydroxyl ions. If so, the 

 action might be suppressed by subsiequent treatment with 

 equivalent alkali after the acid. This is not the case. The 

 treatment very possibly increases the permeability of the seed- 

 coat to oxygen or water, and hence provides the requisite 

 stimulus to germination. This explanation will suffice for all 



1 Landw., Versuchsst, xx., p. 76. 



i Ber. (i. I). Bot Ges., 1907, bd. xxv., p. 108 



