xxvi PREFACE. 
which is, that, in Anthoceros in which the evolution of 
the sporules is carried on in succession, or for a 
considerable period, after those first formed are ma- 
tured, and have escaped; steps are taken to ensure a 
similar gradual succession of the male organs. The 
obvious difference is the apparent effect of the process 
in forming the seta analogous to the formation of pol- 
len in some Aroidea and theca, not being limited as 
in Phanerogame to the evolution alone of the repro- 
ductive sporules or seeds. On these points Valentine 
has read a paper before the Linn Society, containing 
new views, and pointing out abundance of facts hi- 
therto entirely overlooked by Cryptogamists; the an- 
thers have no affinity of structure whatever with gem- 
mz. This is particularly observable in Hepatice. 
Hepatice.—The common structure of the order is 
to have an original theca resembling much, that which 
is called the calyptra of mosses, and indeed differing 
only in never being torn up from its attachment. The 
only exception, I know of, to this occurs in Anthoce- 
ros, which appears not to have an original capsule, 
and consequently no calyptra. That which has been 
called a calyptra being nothing but a mass of tissue - 
dislocated by the growth of the theca, I think also that 
Marchantia can have no caiyptra, with regard to the 
secondary thecz, they certainly present great differ- 
ences; their place is supplied in Riccia by the origi- 
nal theca; are anomaly perhaps dependent on the 
immersion of the theca in the frond itself. 
I have no more doubt about the impregnation of 
this order, than of mosses. The anthers of Anthoceros 
regularly dehisce at their apices, and discharge the mi- 
