44 Scientific Proceedings^ Royal Dublin Society. 



From these results it may be seen that there is no concentration of the 

 solutions, as would be the case if a semipermeable membrane existed. There 

 is, however, a weakening of the solutions due to various causes. In the acid 

 experiments it is due to the alkalinity of the cell substance, as was noticed by 

 A. J. Brown in Hordeum. Experiment 5, however, shows that, on crushing 

 the beans and extracting with hot water, only an amount of alkali equal to 

 0'3 o.c. normal NaOH was found derived from one hundred beans. The 

 extract was boiled to expel CO2 before titrating. 



In the case of the undesiccated seeds, some of the weakening of the acid 

 is accounted for by the moisture of the seeds diluting the solution. This is 

 evidence in favour of the permeability of the seeds. The diluting effect does 

 not, of course, occur in experiment 4 with desiccated beans. To ascertain 

 whether the seeds weakened the acid by uuextractable. alkali, or by con- 

 centrating the solution in themselves, the seeds used in experiment 3 were 

 drained, leaving 48 c.c. of weak acid, corresponding to an absorption of 

 52 c.c. of acid solution. 37 c.c. of normal acid was found in the beans, 

 though they had absorbed 52 c.c. of normal acid, besides weakening the 

 remaining 48 c.c, so that it only contained 38'8 c.c. of normal acid. This 

 gives 75'8 c.c. of normal H2SO4 remaining ; 24-2 c.c. must therefore have 

 been neutralized by the bean-cell substances, or, allowing for the dilution 

 effect as a maximum of 10 c.c, 14'2 c.c. was neutralized, as in experiment 4. 

 This gives 0'142 c.c. of normal H2SO4 per bean, viz. 0*007 grm., or 1"47 per 

 cent, of tlie weight of desiccated bean-substance. 



The sodium chloride was practically unchanged, the dilution only being 

 sliglit, as traces of chloride were foiiud in experiments 7 and 8, having been 

 washed out of the seeds. The chlorides initially present prevent the dilution 

 being noticeable. In the iodine experiments, microscopic examination 

 showed that all parts of the seed were penetrated by the iodine ; the solution 

 was decolorized by the formation of large quantities of starch iodide. 



Thus none of the facts ascertained give any reason to believe in the 

 presence of a semipermeable membrane in dry seeds absorbing water in 

 their initial stages. 



In experiment 11 the seeds used had all taken up about 140 per cent, of 

 their dry weight of water, and had just put forth radicles. They were dried in 

 a warm room, about 15° 0. for tliree liours, and then placed in the salt solution. 



A dilution effect was noticed amounting to 0'92 of the original con- 

 centration. But as the hundred beans contained about 65 c.c. of water, if 

 they were completely permeable, the dilution should have been \^ = 0-61. 

 So here semipermeability is met with, though it is not absolute. Evidently 

 the protoplasm in the growing living cells is the semipermeable substance. 



