1906] CROCKER—DELAYVED GERMINATION 287 
TABLE Xs 
| I | II 
| 
1. Ax yrs AMarantnoides <<... 55 2-16 ayes es, | 100 | ° 
2. Xanthium pennsylvanicum.............-.... gos 5) 5° 
3 alaspi CONSE. AAS eS eee | kere) 57 
4. Blantago Rupelli. oo oc. ee 96 4 
5. Avena fatuad 2. oo a ene a 96 | 75 
6. Piantago major.<'. > +4 sein < Deco ee ek 905-4) 24 
%, Chenopodium album: ¢. 0 +.<..., 5. 6s ee | 100 | 67 
tion for the seven species tested is 98 per cent. with seed coats rup- 
tured, 40 per cent. with seed coats intact. It may be urged that the 
seeds used by Duvet are of low vitality. This, however, does not 
seem at all probable, for I obtained only slightly higher percentages, 
as shown in Tables VIII and IX, with the coats intact and with 
favorable temperatures, than those reported by Duvet. These 
slightly higher percentages can be accounted for by the fact that the 
temperature used by me was 28-33°, while the temperature used by 
DUVEL was 20-30°, Two species of seeds mentioned in this table 
need special consideration. In Axyris amaranthoides, DUVEL deter- 
mined the vitality as o per cent. This is exactly what would. be 
expected if form 6 alone (as shown in Table IX) were used, and if 
the effect of the seed coat were overlooked. In Xanthium pennsyl- 
vanicum he finds so per cent. germinating. This, too, is what would 
be expected if the upper and lower seeds of the cocklebur were put 
in a germinator at 20-30°. The lower seeds would germinate in 
this condition and the others fail to do so. It seems probable, then, 
that in Xanthium and Axyris Duvet overlooked the dimorphic 
character of the seeds, as well as the effect of the coats on germina- 
ion. Vitality tests of this kind, that neglect the effect of the seed 
“oats, are tests of the condition of the seed coats rather than tests 
of the real vitality of the embryos themselves. It is evident that if 
these errors appear in the original tests for vitality they will likewise 
‘ppear in the tests made after different periods of burial. If vitality 
tests, looking to the extermination of weeds, are to be of real value, 
the ©xact germinative character of each species must first be deter- 
mined, and all vitality tests must then be mide on the basis of these 
Serminative characters. : 
