373 _  CRYPTOGAMIA; 
{e.) Gills in pairs. 2 i al 
(f.) Gills 4 in a set. : io Seeriae 
ts.) Gills 8 in a set, ‘ : + Sigal 
{b.) Gills irregular, that is, no determinate number ina 
set ; tee 
(i.) Gills branching. | 
(k.) Gills branching and anastomosing. dot 
C, Gills loose from the stem, but the inner end fixedto a 
— Collar which surrounds the top of the Stem, — 
_ though not in contact with it. ; TB oe 
These various circumstances of the’ Gills seem at first : 
sight well adapted for subdivisions of the species, and also 
for the formation of ‘specific characters ; but they areso 
much subject to variation, that no use can be made of them , 
for either purpose. Thus, the Gills called wniform, are 
seldom strictly so, a shorter Gill now and then interve 
ing. The Gills in pairs have place only in’ a few spec 
and are subject to vary ; the Gills 4 in a set, occupy 
far the greater part of the species, and those which ha 
4 in a set in the younger plants, are very apt to shew 
when more fully expanded, some of the longer Gills te 
ing from the Stem. Moreover, though 4 in a set be the 
ominant number in many oft 1ese plants, we often find ser 
ut three, or even two, owing to the absence of one or more 
of the smaller Gills. “The colour of the Gills is fortunat 
an obvious, and at the same timea permanent cir umstan 
and when we reflect; that their colour is principally, # 
not solely, caused by that of the Fructifications or Seeds fe 
within them, we might (a priori) have expected, what 
experience has taught me to be the case, that it js, the most 2 
fixed, the most certain characteristic, on which to foun¢ 
the distinctions of the species; and that this, together with - 
the structure, will be at all times sufficient to afford ae 
manent specific distinctions. It is allowed that these ¢0 
lours change when the plant begins to. decay, but 
Botanist would complain that the characters are W 
in a subject sellertad in a rotten state. The colour © 
Jat sides of the Gills is what I wish to be attended to, be 
cause the colour at the edge, in some plants, is differen 
through all the stages of growth, and in others it chi 
sooner than that of the = 0 evidently from the dischal 
of the Seeds when ripe. The colour of the whole of the 
being sometimes te by the ripened Seeds, it 18 © 
