
192° BOTANICAL GAZETTE [SEPTEMBER 
embryo, not much above normal in size, surrounded on. all sides by - 
a liquid which is held in by the semipermeable membrane. 
This curve is of great interest in connection with FISCHER’s 
(16) work on the seeds of water plants. When the seeds have a 
brittle instead of an elastic coat, the pressure from within may be 
great enough to rupture the coat, and allow oxygen or some other 
requisite for germination to enter. There is no doubt that this 
actually happens with acids and alkalies in the case of Alisma 
Plantago-aquatica, one of the seeds which FISCHER stimulated with 
hydrogen and hydroxyl ions, and which CROCKER (15) showed at 
the same time needed only to have the coat broken to bring about 
germination. In view of the effect of certain acids and alkalies on 
seeds with semipermeable coats, the reason for germination on 
treatment with these substances is obvious. 
In this connection sight must not be lost of the possible effect of 
acids, alkalies, etc., on the colloids of the seed. FiscHER (17, 18) 
has shown the remarkable effect of acids and alkalies on the water- 
holding power of fibrin and frog mnscle, and has pointed out the 
relation of acids to edema and glaucoma (19). A part of the 
increased weight may be due to the colloids in the embryo holding 
more water in the different states of ionization induced in them by 
the presence of acids and alkalies ; but most of it is certainly due 
to the osmotic pressure from within, which adds a large quantity 
beyond what capillarity and imbibition would take up. 
The behavior of the coat in retaining dissolved substances adds 
further evidence to that already brought forward to show that even 
after prolonged treatment in tannin solvents the coats are still 
semipermeable. 
The high internal forces in dry seeds is interesting in connection 
with recent work on the osmotic pressures of the cells of desert 
plants. Frrrinc (20) shows that desert vegetation has in many 
instances cell sap with more than 100 atmospheres of pressure, an 
adaptation which is of great importance to the plant whose “‘satura- 
tion deficit” must withdraw the water from an arid soil. The value 
of Firrine’s work would have been enhanced if he had used boiling 
or freezing-point methods as a check to the plasmolytic methods of 
determining the osmotic pressure. The possibility suggests itself 
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