GENERAL REMARKS. 209 
lip is not represented as distinct from the plumule, see pl 
6. 11. 13. 
Calla differs from Acorus in this, that the perianth is con- 
verted into stamena, to this there is a considerable tendency 
in Acorus itself. 
I consider the objection which might be raised to my re- 
garding it the radicle on account of the direction of the plu- 
mule, weakened by the direction which this assumes in most 
Aroidee. 
It should not be forgotton either, that a section of the seed 
accords entirely with that of Monocotyledons, and were it 
not that the subsequent evolution indicates so plainly the na- 
ture of the part, we might consider the plumule as the radi- 
cle, and the gemmæ as the plumule, the chief difference con- 
sisting in the radicle being already distinct. 
Stomata appear to have been known to L. C. Richard who 
describes fronds as minutissima creberrimeque porulosa on 
their upper surface. 
The origin of the parts has been accurately described by 
Richard. In describing the roots he makes out that 
their direction depends on the gibbosity of the frond, and 
hence it may be inferred were it not for this, that the rvot 
would have an opposite direction to the axis itself. 
It would be desirable to examine whether young fronds are 
opposite, or whether the spathe is opposite to the frond, as 
well as to its relation with the frondule of the same side, 
and why are roots fascicled in some. 
Neither Pistia nor Lemna agree with the character of the 
order as given by Dr. Lindley in his Introduction. As 
Pistia has evidently a much higher, as well as a much more 
distinct organisation than Lemna, it must either form the base 
of a distinct group, or revert to its original station, in Aroidee, 
from which it does not differ in any more essential particular 
than the absence of a lateral slit for the emission of the plu- 
mule. 
Pistia agrees with some Aroidez, as Spathicarpa, in the 
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