32 
provided, and plenty of proof that this does take place. The 
plants have two strings to their bow, and one or both may be 
used as a means of securing offspring, as in many Naiadacee both 
propagating buds and seeds are produced, so that if one method 
fails the other may be employed. It is not always true that the 
pollen is so firmly agglutinated that its grains can be separated 
only by a considerable force. In Lepéorchis, for instance, the 
pollen masses are very loosely granular, without caudicles, glands 
or connecting threads, and the grains are easily detached by the 
wind or rain, and therefore liable to be conveyed to their own 
stigma by such agitation. What serves to show that in this genus 
self-fertilization is common is the fact that our two species produce 
an abundance of ripe capsules which is not generally true in other 
genera where insect agency is absolutely necessary. JL. /iliifolia 
frequently occurs in our Northern woods and nearly every plant 
that I have collected in the latter part of the season is well fur- 
nished with fruit. This is equally the case with the several species 
of Achroanthes. In several of the genera which are destitute of 
caudicles and glands, I have had occasion to observe the pollen 
dust scattered over the lip, column and stigma precisely as I have 
seen the pollen of willows scattered over the inflorescence, suggest- 
ing an analogous distribution. Another very interesting method 
of self-fertilization is related by Sir Jos. Hooker in a paper which _ 
he read before the Royal Society of London, in 1854. The plant 
which he has under review, is Listera ovata, a British species very 
like our L. cordata. He found that if the rostellum is touched or 
irritated when the pollen is ripe a sort of explosion occurs and | 
two white viscid masses are instantly protruded, one from each 
side of the apex, which coalesce and attach themselves to the 
bases of the pollinia, and draw them out of their cases. The 
pollen, he says, is by this means broken up, and the grains fall — 
over the edge of the rostellum upon the stigmatic surface. Here 
is a case which, while not at all preventing the plant from being 
fertilized in the ordinary way by insects, clearly shows that the 
means of self-fertilization is specially provided for. Now in the 
allied genera, Gyrostachys, Peramium, Epipactis, Cathea, Arethusa — 
and Pogonia, while no irritability of this kind has so far been ob- s 
served, yet the caudicular discs are attached so firmly to the back _ 
