378 REV. GEORGE HENSLOW ON THE 
gynous and wind-fertilized, but at others self-fertilizing by the pistil being slightly 
delayed in its development. 
Sueda maritima. The order of development of this plant is—calyx, pistil, stamens; 
but the stamens outgrow the pistil, curve over it, and dehisce while the lobes of the 
calyx remain more or less unexpanded. It is thus self-fertilizing. 
PoLYGONACE®.— Polygonum is a genus affording considerable differences in the 
sexuality of the species. P. Fagopyrum Müller has shown to be dimorphic, and P. Bis- 
torta proterandrous; but I find P. Persicaria, P. aviculare, and P. Convolvulus and 
P. Hydropiper are all self-fertilizing. P. Persicaria secretes a little honey,but insect-visits 
are probably very rare; so that it may represent an intermediate condition between 
intercrossing and purely self-fertilizing forms. P. Convolvulus and P. Hydropiper appear 
to be always cleistogamous, at least I have never seen the perianth expanded. The 
stamens all arch over the pistil, and the anthers cover the stigmas with pollen. 
EvPHORBIACE.—Mr. Bennett found that Euphorbia Helioscopia and E. i. Peplus were 
self-fertilizing, i. e. if we may use the expression for the moncecious inflorescences of these 
plants. Other species, such as E. amygdaloides and some tropical forms, with brilliantly 
coloured bracts or glands, are strongly proterogynous. | 
MOoNOCOTYLEDONS.—l have not made many observations on plants of this class; but 
ihe same principles appear to hold good, namely, that conspicuous flowers are adapted 
for intererossing by insects, but inconspicuous ones are either self-fertilizing or anemo- - 
philous. : 
OncurpACE E.—Mr. Darwin has recorded that Ophrys apifera is highly self-fertile, and - 
is therefore an exception to the rule, of a conspicuous flower being not crossed by insects. 
Cephalanthera grandiflora is also described by that author as a case of “ perpetual self- 
fertilisation, but in an extremely imperfect degree" (Fert. of Orchids, p. 111). ps 
If we ask why the Bee Ophrys is so prolific, is one of the most abundant and vigorous : 
of Orchids, and is yet perpetually self-fertilized, I presume the answer would be that it 
is descended from an intererossing form which was crossed, and that the benefits of the ` 
cross have been inherited and become permanent, so that it no longer requires any more - 
extraneous aid. This, at least, is Mr. Darwin's argument to account for Andrew Knight's | 
varieties of Peas lasting for 60 years, though regularly self-fertilized (Cross &c. p. 305). 
My reply is that the entire argument is an à priori inference, based upon the. supposed 
necessity of crossing. It is an argument which, from the nature of the case, cannot be 
proved. On the other hand, none of Mr. Darwin’s experiments countenance the idea 
that the effects of crossing are permanent; whilst in many cases plants which either are ` 
habitually self-fertilized, or have acquired self-fertilization, showed great indifference to 
being erossed, and were, in fact, vastly superior to their intercrossed competitors. More 
over, plants like Polygonum Convolvulus, P. Hydropiper, and Hordeum murinum are, as | 
far as I have observed them, habitually cleistogamous, the flowers never expanding, and en ` 
cannot be crossed. Hence my argument that crossing is superfluous for all such plants ` 
is equally, if not more, pertinent. (See remarks under Ipomea and Mimulus, p. sag | 
 AXISMACEA.—4lisma Plantago. This plant appears to me to resemble Agrimo 
in daos at first Late for eres ne the anthers spr A 
