84 
G. P. DARNELL-SMITH ON 
length ; this slit, from which the prothallium later emerges, is bounded on either side 
throughout its length by a thick smooth lip (fig. l). 
On placing the spores in water the depressed areas adjacent to the ridge swell 
somewhat, and the ridge in consequence becomes less marked. Spores thus treated 
have almost the same specific gravity as water, a point not without significance, as 
they germinate below the surface of the ground, and, being of about the same specific 
gravity as water, they are liable to be carried further by it than if they either sank 
or floated. 
Spores placed in water or in any medium unsuitable for their germination usually 
show in time a vacuole at each end, with the protoplasm collected around the nucleus, 
which is central, forming an irregular band transverse to the length of the spore 
(fig. 3). Spores placed in an environment suitable for germination show in a few 
days a central nucleus surrounded by numerous circular droplets which completely 
fill the cell (fig. 2). In this condition the spore may remain from four to six months. 
Seen in the mass the spores are of a faint yellow colour. When placed in a small 
heap upon blue litmus paper and moistened, they give a slight acid reaction. In the 
presence of ammonia vapour they turn a brilliant orange colour. If heated at 70° C. 
for some time, the cytoplasm turns a greenish brown and the nucleus becomes dark 
brown. 
After repeated failures with a large variety of expedients I succeeded in causing 
the spores to germinate in the laboratory and in the field. The chief reasons of 
failure in my earlier attempts may be summarised as follows : — (l) Using sterilised 
soil in which the endophytic fungus would not be present ; (2) using spores that 
were too old or not absolutely mature ; (3) keeping the spores too wet with stagnant 
water; (4) failure to provide adequate drainage; (5) failure to provide a rigid 
surface above and below the spores. 
I have succeeded in growing spores in the laboratory as follows : — 
(a) In earth placed between two flat pieces of sandstone. These were placed on 
pieces of rock in a porous earthenware butter-cooler consisting of two circular 
chambers. A central one, in which the rocks were placed, had holes in the bottom to 
provide drainage ; it was surrounded by another concentric chamber, the bottom of 
which was intact. Water was placed in this external chamber, and was replaced 
frequently as the supply passed away through the porous earthenware. Both 
chambers were covered with a lid. The air in the central chamber was thus always 
saturated with moisture. The frequent seepage and renewal of the water seems to 
be especially valuable in obtaining freedom from moulds, which, where the water is 
stagnant, are frequently a nuisance, though the spores of Psilotum appear to be more 
or less immune, even when moulds are present. 
( b ) By the removal, from the vertical side of a rock in the open, of a mass of 
soil and debris felted together by roots, and fixing it by wire to a rock placed 
vertically in a case in the laboratory. 
