570 Mr. HenveErson on the Reproductive Organs of Equisetum. 
water, they are found to consist exclusively of the lesser granules, the larger 
ones having now altogether disappeared. As the spore swells, the divisions of 
the integument are forced asunder; a portion at each end however generally 
adheres longer, and preserves the form represented at Tas. XXXIX. fig. 10.; 
and although further separated, these divisions are still held in their spiral 
position until the ripening of the spore, when, being ejected from the theca, 
they recoil with a jerk, and immediately twist into narrow clavate filaments, 
the state in which they have been most frequently observed. "Tas. XXXIX. 
fig. 12. represents the spore previous to its ripening and to the opening of the 
theca; the filaments are partly unrolled, and their attachment to the spore 
and to each other is shown. 
In the ripened state the spore has a wrinkled or plaited appearance, arising 
from some peculiarity in its immediate covering, which appears to add greatly 
to its opacity. On the application of water to the spore, it immediately swells 
to considerably beyond its original size, the wrinkles on its surface disappear, 
and it changes to a bright green colour. By adding tincture of iodine to 
the water a very curious effect is produced, which proves the existence of an 
outer and inner membrane or tunie to the spore: its nucleus is contracted 
to a much smaller size, leaving the outer membrane occupying the space to 
which it had been distended by the water, and appearing under transmitted 
light like a transparent limb to the opake spore (Tas. XXXIX. fig. 13.). The 
spore on arriving at maturity acquires a dark green colour ; it contains a thick 
viscid fluid, copiously mixed with minute granules exactly similar to those 
contained in the pollen-grains of flowering plants; they seem not to differ 
greatly from, if they are not identical with, the lesser granules found in the 
integument and in the intercellular cavities of the theca. The larger granules 
having all disappeared immediately after the separation of the integument, it 
would appear that their functions are somewhat different from those of the 
lesser ones; the former, I have no doubt, are of an amylaceous nature, being 
soluble in boiling water, but not in alcohol. I inclosed some spikes of Equi- 
setum hyemale, in that state when the granules of both kinds are most nume- 
rous, in a phial with water; the phial was then held in a vessel of boiling 
water for half an hour, and on examining the thecæ, I found that the larger 
granules had all disappeared, but that the lesser ones remained unaltered, 
