Germination of Arceutkobium occidentale . 103 
attraction of water into this layer sets up a turgescence which could not be 
measured, but which probably amounted to many atmospheres.' In 
A. occidentale we see that it is the imbibition of water by the material of the 
cell-walls rather than the osmotic activity of the cell-contents which brings 
in water ; that the water is taken up and held by the swelling gelatine of 
the walls. What the resulting pressure amounts to is unknown, and may 
for the present remain unguessed. 
Finally, the pressure within the fruit becomes too great, under the con- 
ditions which I have described, and, with or without some jar to set it off, 
the fruit breaks at the base. The conical shape of the ‘seed,’ with the 
larger end at the back, gives it a cumulative impulse from the top and sides 
of the fruit, the sides compressing and indirectly propelling it, the top pro- 
pelling it directly since, before the fruit breaks, much of the pressure has 
been against the tough epidermis and the lignified layer at the top, stretch- 
ing these upward. 
Passing now to the * seed.’ Morphologically this is a seed enclosed in 
the inner part of the ovary (Engler and Prantl). The greater part of it is 
covered with a gelatinous layer sticky enough to attach it to smooth objects 
as well as rough. This layer will take up still more water from damp 
air, swell, and so come into contact with a still more extended surface than 
it at first touched. Furthermore, this gelatinous material dries only very 
slowly even in dry air. But damp air, only moderately cool, is necessary 
for germination. 
The structure of the ‘ seed ’ is essentially as described and figured by 
Johnson (1888), but as A. occidentale appears to differ somewhat I may give 
some details. The gelatinous outer layer (see Fig. 7, a ‘ seed ’ fixed in dilute 
Flemming’s solution, and Fig. 12, a longitudinal section of an ungerminated 
‘seed’) consists of much-elongated cells, their much-thickened walls con- 
sisting of two layers (Fig. 8), an outer of gelatinous material, an inner of 
cellulose spirally thickened. The cell cavity is very narrow. These long 
cells are attached obliquely or at right angles to cells of the sclerotic layer 
of the ‘seed.’ On the outside (as Fig. 8 shows) ‘dirt’ of all kinds may 
adhere. Figures 9 and 10 show the extent to which these gelatinized 
cells may expand. Figure 9 shows a cross-section of these cells near the 
tip, tangential to the seed, which had lain for some weeks in 95 °/ o alcohol. 
Figure 10 is the outer part of the same section after it had lain for a quarter 
of an hour in water on the slide. 
With the slow loss of water which takes place as the air dries, these long 
cells, attached at their tips to whatever the ‘ seed ’ has struck, and at their 
bases to the firm sclerotic coat, contract, shorten. Owing to the spiral thick- 
ening of the inner cellulose wall, the shortening of these cells pulls the ‘seed’ 
closer and closer, and attaches it more and more firmly, to whatever it has 
struck. This attachment may hold for many months, for I have seen ‘seeds’ 
