SEXUALITY OF PLANTS. 829 
more commonly do, they arise as little projections on the top of 
the ring, the number of which corresponds to the future divisions 
of the calyx or corolla. 
All irregular calyces or corollas are regular at their first 
formation, the cellular papille from which they arise being all 
equal in size; hence all irregularity is produced by unequal 
subsequent growth. 
2. FUNCTIONS OF THE ESSENTIAL ORGANS OF REPRODUCTION. 
Sexuality of Plants. —Though vaguely suspected by the ancients, 
the true sexuality of plants was not definitively ascertained till 
1676, in which year Sir T. Millington, of Oxford, determined the 
real nature of the stamens. The andrcecium of flowering plants, 
as has been already repeatedly stated, constitutes the male 
apparatus, and the gyncecium the female. That the influence of 
the pollen is necessary to the formation of perfect seed is positively 
established. 
While the presence of distinct sexes may thus be shown in 
flowering plants, both of which are necessary for the formation 
of perfect seed, by far the greater number of flowerless plants, 
in like manner, as we have seen, possess certain organs the 
functions of which are undoubtedly sexual. It is quite true 
that the existence of sexuality has not been absolutely demon- 
strated in all the Cryptogamia; but as it is known to exist in 
the greater number, we may fairly conclude from analogy that 
it is present in all. 
We have already, as fully as our space will permit, described 
the structure of the reproductive organs of both the Phanero- 
gamia and the Cryptogamia; we now proceed to give a general 
summary of the more important conclusions which have been 
arrived at as regards the process of reproduction in the several 
divisions of plants, and in doing so we shall commence with the 
Cryptogamia. 
1. REPRODUCTION OF THE CryproGcAmia.—In describing the 
structure of the reproductive organs of these plants (see pages 
363-399), we treated of them in two divisions, called, respec- 
tively, Cormophytes and Thallophytes, each of which was again 
subdivided into several natural orders. We shall follow the 
same arrangement in describing their modes of reproduction, 
except that we shall here commence with the Thallophytes, and 
proceed upwards to those plants of a more complicated nature, 
instead of alluding to them, as we then did, in the inverse order. 
A. Reproduction of Thallophytes.—The sexual method of 
reproduction (gamogenesis) of all Thallophytes has not been 
absolutely proved, but only concluded from analogy, though the 
asexual or vegetative mode (agamogenesis) obtains in all. Sexes 
have been clearly shown to exist in certain Algz, Fungi, and 
Lichens ; and generally in Characez. Oérsted, indeed, has 
described the impregnation of oO0gonia on the mycelium of 
Agaricus; but other observers have failed to verify his asser- 
