result from the conditions to which the plants have been subjected, and partakes
of the nature of a monstrosity. All the flowers on the same plant are commonly
affected in the same manner. Such cases, though they have sometimes been ranked
as cleistogamic, do not come within our present scope: see Dr. Maxwell Masters
'Vegetable Teratology' 1869 page 403.) They are manifestly adapted for self-
fertilisation, which is effected at the cost of a wonderfully small expenditure
of pollen; whilst the perfect flowers produced by the same plant are capable of
cross-fertilisation. Certain aquatic species, when they flower beneath the
water, keep their corollas closed, apparently to protect their pollen; they
might therefore be called cleistogamic, but for reasons assigned in the proper
place are not included in the present sub-group. Several cleistogamic species,
as we shall hereafter see, bury their ovaries or young capsules in the ground;
but some few other plants behave in the same manner; and, as they do not bury
all their flowers, they might have formed a small separate subdivision.

Another interesting subdivision consists of certain plants, discovered by H.
Muller, some individuals of which bear conspicuous flowers adapted for cross-
fertilisation by the aid of insects, and others much smaller and less
conspicuous flowers, which have often been slightly modified so as to ensure
self-fertilisation. Lysimachia vulgaris, Euphrasia officinalis, Rhinanthus
crista-galli, and Viola tricolor come under this head. (Introduction/4. H.
Muller 'Nature' September 25, 1873 volume 8 page 433 and November 20, 1873
volume 9 page 44. Also 'Die Befruchtung der Blumen' etc. 1873 page 294.) The
smaller and less conspicuous flowers are not closed, but as far as the purpose
which they serve is concerned, namely, the assured propagation of the species,
they approach in nature cleistogamic flowers; but they differ from them by the
two kinds being produced on distinct plants.

With many plants, the flowers towards the outside of the inflorescence are much
larger and more conspicuous than the central ones. As I shall not have occasion