60 Bergtheil and Day . — ‘ Hardness ’ in Seeds of Indigofer a. 
It would be of interest to determine whether this latter method of 
treatment would answer in other cases of hard seed, and whether their 
hardness can be traced to a similar cause to that which has been de- 
scribed. 
Literature. 
1. H. M. Leake : Journ. Royal Hort. Soc., vol. xxix. 
2. J. Percival : Agricultural Botany, p. 623. 
3. A. Zimmerman n : Die botanische Mikrotechnik, p. 138. 
4. : Ibid., p. 149. 
Since writing the above we have seen a paper by Jarzymowski 
(Inaugural-Dissertation, Halle, 1905), dealing with hardness in several legu- 
minous seeds. This author holds that hardness is conditioned by the size 
of the lumina in the cells of the c palisade ’ layer of the seed-coat. This 
explanation does not apply to the case of Indigofera arrecta. No difference 
can be detected between the shape or size of the lumina in such cells 
in the coat of this seed and in that of Indigofera sumatrana , nevertheless 
the former hardly germinates at all without treatment, and the latter 
germinates freely. The presence of the hard layer which has been de- 
scribed in the hard variety and its absence in the variety in which hard 
seeds do not occur, seems to point clearly to this being the determining 
cause in this case. 
Jarzymowski has tested the method of treating hard seeds with sulphuric 
acid on several varieties and finds it to answer well ; it appears to have been 
first suggested by Hiltner in 1902. 
