ENALUS ACOROIDES. 
285 
difference in tlie organization of the flower it may be noticed 
that the spathe leaves in Vallisneria are little developed and 
always submerged ; that the flower is kept floating always 
in a vertical position by the relatively well-developed sepals. 
The petals of Vallisneria are very little or not at all developed, 
which is explained by Kerner as an adaptation for the 
exposition of the stigmas. These are placed betiveen the 
sepals, so that they can be easily reached by the anthers 
if the petals are reduced. And as regards the male flowers 
in Vallisneria the anthers have rather long filaments 
obliquely stretched out, so that the anthers can come into 
direct contact with the stigmas. 
In all these respects Enalus is opposed to Vallisneria. A 
superficial comparison shows that the petals are developed 
as organs to catch the male flowers ; that the pollination is 
arranged by the changed position (due to the tides) of the 
flower, which is horizontal on the surface, but vertical below 
it ; the filaments in Enalus are quite reduced, so that a direct 
transport of pollen from the anthers, which besides are 
directed straight upwards, is impossible. The pollen grains 
are also heavier than water, and therefore they can scarcely 
reach the stigmas by floating. Finally, all these differences 
must be considered in relation to the fact that Enalus is a sea 
plant exposed to the differences of the tide , which cause a 
periodical change in the exposition of the female and loose¬ 
ning of the male flowers. Vallisneria, on the contrary, is a 
lake plant without any such changes in the level of the 
surface. 
The Ripening of the Fruit and the Development off 
the EmSsryo. —After the pollination and fertilization the 
fruit is pulled down to the bottom by the spiral twisting of 
the pedicel, just as in Vallisneria (PI. XXIV., A, fig. 14). 
Regarding the real nature of this movement, and what it is 
really due to, very little is known, except that it belongs to 
the “ autonomous movements.” J. F. Müller (21) in his 
paper on Vallisneria has examined the anatomy of the pedicel 
8(10)04 (20) 
