492 Mr. VALENTINE on the Structure and Development 
connexion with this subject I shall take the opportunity of observing, that 
from a partial examination of Lycopodium and Isoétes, I believe Dr. Lindley. 
is also correct as to the pulverulent matter of those genera being abortive spo- 
rules. I at first intended to add to this paper some general observations on 
the several groups which compose the Cryptogamia of Linnæus, but I now 
think it more desirable to defer this until they have been separately submitted 
to examination; for without an accurate knowledge of their structure and 
germination, it is impossible to arrive at a satisfactory conclusion as to their 
affinities. I cannot help observing, however, that Dr. Lindley has not in my 
opinion exercised his usual judgment in removing Lquisetacee from Acrogens 
to Gymnosperms. The affinity which they have to the latter is entirely in their 
aspect; there is no obvious structural or physiological analogy between them. 
The supposition of Brongniart, that the reproductive body is a naked ovule, 
and the four filaments that surround it four grains of pollen, without the power, 
according to Lindley, of perforining their function, is contradictory ; for what 
evidence have we of any fertile ovule without the agency of the male organ? 
Besides, this supposed ovule is admitted in the same paragraph to be a sporule, 
and afterwards proved to be such by its germination. 
This account of Pilularia shows that it is incorrect to say of Acrogens that 
“ germination takes place at no fixed point, but upon any part of the surface 
of the spores ;” for it is quite certain in this instance that germination in- 
variably takes place at a fixed spot, which may be pointed out before germi- 
nation has commenced. It is at that part of the sporule indicated by the 
three radiating lines which appear to have been produced by the pressure of 
the three other sporules that originally helped to constitute the quaternary 
union ; and as the spores of all the other tribes appear, according to Mohl, to 
be developed in similar unions, it is most probable that similar lines indi- 
cating a valvular dehiscence also exist on them. This is certainly the case in 
some Mosses, for instance, in fEdipodium, and in Isoétes, Lycopodium, and 
Osmunda regalis ; and in those instances Where such a structure is not visible, 
it is probably owing to a thickening of the membrane, or a deposition of 
opake matter on its surface, as in Pilularia. Yn the mature sporules of Pilu- 
laria they can only be discovered by dissection, and in the abortive ones they 
cannot be discovered at all after the fivst stages of their growth ; whilst, again, 
