effectively under water. Then the stalk of the pistillifero 
192 FECUNDATION. 
grass of Parnassus, the stamens are endowed with a motive 
power of this sort. 
467. In moneecious (289) plants, the male flowers are fre- 
quently situated on the upper part, so that the pollen falls — 
on the stigma. In these and in dicecious (289) plants, the © 
wind is perhaps the chief agent in conveying the pollen, — 
which is a light powder, from the male to the female flowers; 
and butterflies and other insects which fly from flower to 
flower also carry and deposit the pollen. In Persia, the 
female or fertile Palms chiefly are cultivated, and at the 
flowering seasons branches of Wild Palms with male flowers 
are gathered and shaken over the fertile flowers. This 
was practised long before the theory of the operation was 
known. 
468. In a dicwcious plant which grows under water 
(Valisneria spiralis), the antheriferous flowers become de- 
tached, rise to the surface, and float about, while the pistil- 
liferous flower, which retains its connection with the plant, 
has a spiral stalk, which unfolds and lengthens out so as to 
elevate the flower above the surface of the water. There 
the two kinds of flowers meet, and insects or the wind apply 
the pollen to the stigma, an operation which does not go on 
flower resumes its spiral form, and draws the flower under 
_ water, there to perfect the seed. The Utricularia, a plant 
which grows under water, and has perfect flowers, has blad- 
_ ders attached to its roots, which become filled with gaseous 
matter, so as to cause the plant to ascend to the surface 
_ when the pollen is ripe, and effect the application of the pol- 
_ lenin the air. When this is done, the bladders lose their 
