THE GAMETOPHYTE OF PSILOTUM. 
85 
Psilotum spores were shown between the rock and the felted mass, and the soil 
was kept moist as follows : — 
A vessel containing water was placed above the case containing the rock, and from 
it a piece of rubber pressure-tubing, -f-inch in diameter with an internal bore of -g-inch 
diameter, was led in a horizontal direction above the rock and the distal end closed 
with a pinch-cock. Half a dozen pieces of fine capillary glass tubing 1 inch long were 
fixed at intervals in holes in the thick wall of the rubber tubing, in such a manner 
that their ends abutted on the distal side of the internal wall of the rubber tube. 
The tube was used as in the manner of a siphon, and by adjusting the distance 
between the internal ends of the capillary glass tubes and the wall of the rubber 
tube it was possible to obtain a continuous “ drip ” of water at any desired rate. 
1 have succeeded in growing spores in the field as follows : — (l) By splitting off 
with wedges in a suitable locality a large slab of rock, separated from another by a 
fissure, dusting the spores gently from the flattened end of a platinum wire upon 
the thin layer of soil exposed, and replacing the slab. (2) By cutting a thin slit in 
a piece of pumice with a fret-saw, smearing it with earth, dusting spores into the 
slit, and forcing the piece of pumice so treated into the earth in a rock fissure. 
(3) By cutting thin sections of dense sponge, dusting spores between two sections, 
and forcing the pieces of sponge with a scalpel into a damp rock fissure. The value 
of this method is that the spores can be easily found again for examination. (4) By 
removing the surface earth from a rock fissure, blowing spores from the end of a 
flattened platinum wire into it, and then replacing the surface earth removed. 
To avoid the very tedious process of hunting with a microscope for germinating 
spores in the soil treated in the above experiments, the following process was adopted 
and was found to work well : — 
The soil to be examined was agitated gently with water in a 100-c.c. cylinder. 
On standing, the sand and coarser particles of soil sank quickly and the light particles 
floated to the surface. Some of the clear water was pipetted off ; the germinating 
and ungerminated spores were found to be suspended in it. This water was placed 
in two tubes, the heights in the liquid columns were adjusted to the same level, and 
the tubes were then placed for ten minutes in a centrifuge revolving at a moderate 
speed. The deposit in the tubes could be quickly and easily examined for spores, and 
if any special stage was required for mounting it could be picked out by touching the 
spot of water where it was noticed with a very fine capillary glass tube. The water 
immediately ascended the tube, owing to capillary attraction, and carried the spore 
with it. 
The first stage noticeable in the germination of the spore, which commences 
about four months after sowing, is the protrusion of a small lobule covered with 
a thin membrane through the cleft in the spore. Later the lobule increases in size 
and the membrane (intine) becomes more attenuated. Near the apex of the lobule, 
but slightly on one side, a number of small yellowish-brown patches (probably 
