464 JOURNAL OF SCIENCE. 
and three carpels. Among Dicotyledons we have seen there was a 
eroup in which no petals appear to have been developed, viz., the 
Apetale, although, as I have said, it is just possible that even in this 
we are wrong, and that all Apetale are derived from flowers with 
petals by a process of degradation. But among Monocotyiedons it 
would appear that all the present imperfect forms are degraded 
from a form furnished with petals. There are three main groups of 
Monocotyledons at present distinguished by botanists, the first two 
of which, termed the Petaloide, are furnished with a tolerably perfect 
whorl of petals, though even some of them, like the Natade (Pond- 
weeds, Duckweeds, &c.), are very much degraded. In one group of 
Petaloide the petals are distinct from and underneath the pistil or 
ovary (//ypogync) asin Lilies; in the other the ovary is enclosed in 
the lower part of the joined petals, which consequently appear to be 
fastened above it, as in Iris and Orchids (Zpigyne). In the third 
group of Monocotyledons, of which grasses and sedges may be taken 
as examples, the petals have become so reduced as in some cases to 
be wanting altogether, and all the flowers show great degradation. 
In these foregoing remarks on classification, I have endeavoured, 
very briefly, to show you the main lines of descent of flowering plants. 
I will now endeavour to show you what I may term secondary lines 
of evolution, and the following-out of which will supply us with some 
of the most mteresting researches in botanical science. You may 
remember how in speaking of pitcher and other insectivorous plants, 
I stated that the habit of utilizing animal matter which had arisen 
independently in several groups of plants, and was not confined to 
any one group. Similarly I mentioned that two genera belonging to 
totally distinct groups had acquired the same peculiar habit of 
parasitism by means of suckers, thus giving rise to a remarkable 
similarity ‘in external appearance among two sets of plants having 
very little relationship with each other. It is such developments as 
these which I term secondary lines of evolution. It is probable that 
the earliest flowers, whether Di- or Mono-cotyledons, consisted of 
eroups of pistils and stamens, and that even after sepals and petals 
were developed, both the sets of essential organs were present. 
Flowers having both stamens and pistils present are still the 
commonest, and they are termed hermaphrodite. But I have said 
that it was no doubt beneficial for plants to have pollen put on their 
stigmas from the stamens of other plants, for we know that at the 
present day cross-fertilization “always results in the production of 
more numerous and larger seeds. Therefore there early arose among 
flowers a differentiation among the sexual organs, culminating at last 
among plants, as it has long ago done in all the higher animals in a 
complete separation of the sexes. But this result has been arrived at — 
in an extraordinary variety of ways, and we can see among our 
common plants to-day, every stage of these various processes. Thus 
there are a number of plants, of which the garden pea may serve as 
an example, which are completely hermaphrodite and self-fertile. If 
we enclose the flowers in such a way that insects cannot get at them, 
they will still set their seeds, and this for generation after generation. 
Still when insects do get at them, or when they are artificially cross- 
fertilized, the seed so produced give rise to an increasingly strong set 
of plants. One of the first attempts to prevent self-fertilization is when 
the anthers and stigmas mature at different times. This character, 
