114 ISABURO NAGAT: 
BECQUEREL, that the dry seed covering is impermeable to dry alcohol, ether, 
and chloroform. 
From the facts we have thus far surveyed, it is obvious that the viability 
of the seed is held by two main facts when it is subjected to extreme 
conditions, namely, the impermeability of the seed covering to certain toxic 
substances is one, and a state of desiccation of the seed is the other. In 
the forthcoming pages, we shall observe them more closely. 
The selective permeability in the seed covering of rice is demonstrated 
as follows. The method used is the same as that used by the previous 
investigators. Grains of known weight are steeped in solutions of known 
concentrations respectively for a definite length of time, and the increase 
in weight of the grains due to absorption of water from the solutions of dif- 
ferent concentration is used as a criterion of semi-permeability, for the 
method is shown to be quite reliable by the different authors (Brown 1907, 
1909, SHROEDER 1910, SHutt 1913). The hulls of the grains are carefully 
removed by the sharp scalpel, for the absorption of water by the hulls 
obscures the results of the ensuing experiments. 
TABLE I. Oryza sativa (“ Chiba-nishiki ”). 
The absorption of water by the grains indicated by increase of weight in percentage. Tem- 
perature 13.5°—17° C. 
re Concent. 1 E 
No nt hones N Na Cl. og Nach Dist. water. 
steeping. 
4.30 2.12 4.60 7.89 
24 13.18 15.08 20.03 
48 15.81 19.42 22.80 
72 17.85 20.12 24.91 
96 19.48 20.25 21.75* 
* At the end of 72 hours, the lot in distilled water is steeped in In NaCl solution. The 
decrease in weight at the end of another 24 hours is shown to be due to the loss of water by 
exosmosis. (cf. Text fig. 1 a). 
