436 POPULAE SCIENCE EEVIEW. 
unions or crossings between stamens and pistils in tbe three 
forms_, six were fertile^ and twelve, more or less, barren. It 
is clear, therefore, that for a flower to produce its maximum 
of good seed it is absolutely essential that tbe pistil of one 
flower should be fertilized by the pollen from another, and 
that unless so crossed little or no good seed is produced. By 
what agency is this intercrossing effected ? The same reply 
which Mr. Darwin has furnished in respect to Orchids he 
again gives for the purple loosestrife, namely, the interven- 
tion of insects. 
Insects are necessary for the fertilization of this Lythrum. During two 
years I kept two plants of each form protected, and in the autumn they pre- 
sented a remarkable contrast in appearance with the adjoining uncovered 
plants, which were densely covered with capsules. In 1863 a protected long- 
s-tyled plant produced only five poor capsules ; two mid-styled plants produced 
the same number ; and two short-styled plants between them produced only 
one. These capsules contained very few seed ; yet the plants were fully pro- 
ductive when artificially fertilized under the net. In a state of nature the 
flowers are incessantly visited for their nectar by hive- and humble-bees, 
and various diptera. 
We cannot enter into the details of the mode by which this 
fertilization is conducted, or how the different points in struc- 
ture are adapted for the perfect fertilization of the plant, 
whence our author justifies himself in the conclusion that — 
insects, and chiefly bees, act both as general carriers of pollen, and as special 
carriers of the right kind. 
A brief sketch, like the present, cannot do justice to the 
claims of any author like Mr. Darwin to be regarded as the 
great stimulator of inquiry and research in a given direction ; 
but we think it will be admitted that no one has done so much 
of late years for vegetable physiology, and certainly no one 
has exercised so great an influence upon the current of thought 
and investigation on the mysteries of species and variation. 
EXPLANATION OF PLATE. 
Fig. 1. Section of flower of Orchis mascula, with floral leaves removed— Z, labeUum j n, 
nectary; s, stigma; r, rostellam ; «, anther. 
Fig. 2. Front view of the same flower — letters answering to the same parts. 
Fig. 3, Pollinium, removed from its cell — p, pollen mass ; c, caudicle; d, viscid disc. 
Fig. 4. Rostelium, with discs embedded therein and lip depressed — c, caudicles; r,rostellum; 
d, viscid discs. 
Fig. 5. Section of Rostelium and enclosed discs — r, rostelium; d, disc; e, caudicle. 
Fig. 6. Pencil, with Pollinium attached — a, when first removed ; b, after depression. 
Fig. 7- Saddle-shaped Disc of Orchis pyramidalis, with pollinia. 
Fig. 8. Section of flower of Spiranthes uutumnalis — the dotted lines indicate the position of 
the labellum and upper petal. 
Fig. 9. Front view of the Stigma and of the Rostelium with embedded disc — d. 
Fig. 10. Sections of flowers of Lythrum salicaria — a, long-styled form; b, mid-styled form; 
sfcort-sty led form. 
i 
