17 
being filled with a watery sap, but the ovules are shrivelled and withered. 
If, however, the stigma receive, artificially or naturally, sufficient pollen 
for its impregnation, the ovary will increase in size, and the ovaries will be 
found converted into seeds, with their proper characteristics. * 
A description of the structure of seeds, and of the differences between 
those of the dicotyledonous and monocotyledonous plants followed ; also 
the distinctions in the stem, leaves, and flowers of these two great classes 
were touched upon. Numerous examples of the different ways in which 
the cotyledons are folded and curled in various plants were eited, and 
illustrated by the seeds of Euphorbia, Atriplex, Pisum, Convolvulus, the 
wall-flower, stock, and. others: The nature and office of the albumen in 
some seeds was also described. 
On the subject of the exterior appearance of seeds it was remarked, that 
the testa or outer covering of the seed often presents markings of very 
great beauty, especially in the smaller ones viewed with a low power of 
the microscope. Some, as the Violets and various species of Myosotis, are 
smooth and highly polished. Several species of Geranium have regular 
hexagonal markings : in the Euphorbias the testa is traversed by ridges, 
forming an irregular pattern. In gome of the Chickweed family the 
elevations are isolated, constituting miniature mountains and valleys. In 
Antirrhinum majus the ridges and depressions are so disproportionate to 
the size of the seed, that it loses all regularity of form, and might be mis- 
taken for a fragment of cinder. These differences are tolerably constant 
in each natural order, though some genera, and even species, may have 
them more apparent than the rest. In the Scrophulariacese many of the 
genera have rough seeds. Such is also the case in the Lamiacse, while in 
the Cruciferse the seeds are smooth ; the Chickweed group having, however, 
some genera with smooth or only slightly roughened testa, while others, 
as before mentioned, have a very irregular surface . 
The methods, by which the distribution of seeds is effected, were noticed 
at some length, and several special instances mentioned. Among these 
were the following : — 
The five seeds of the Geranium family are each enclosed in a carpel 
provided with a long awn, which when ripe curls upwards from the base, 
and finally becomes detached. This awn is readily affected by hygro- 
* Hooker says, "In general, germens whose stigmas have not received 
the pollen wither away without swelling at all ; but some grow to a con- 
siderable size, and in each case the substance of the seed, its skin and everi 
its cotyledons are often to be found, the embryo only being wanting. n 
