BN ALUS ACOROIDES. 
293 
different origin. Thus in Najas (Jonsson, 15, p. 14) it is 
the lobes of the corolla which act as collecting apparatus, 
in Zannichellia (Goebel, 10, II., 2, p. 365) it is the funnel- 
like stigma itself. In these respects Enalus apparently 
agrees with the hypohydrogamics whose pollen grains are 
heavier than water and are collected by a special “ appareil 
collectenr this in Enalus is effected by the erected funnel¬ 
like group of the twelve stigma lobes (PI. XXIV., A, fig. 9, 
10 ). 
Very characteristic of Enalus, and which makes this plant, 
a very singular pollination type, is the part which the 
petals take in the pollination, viz., as collecting apparatus 
for the male flowers. Afterwards the sinking pollen grains 
are collected by the funnel-like stigma apparatus. Am ong 
the Hydrocharitaceae the genera Blyxa and Limnobium also 
have long and narrow petals like Enalus, but the pollination 
of these plants has not been observed. 
Thus Enalus acoroides takes a singular intermediate 
position among the hydrophilous plants, as it is epihydro- 
gamic in that the male flowers on the water are carried to 
the female flowers, but hypohydrogamic in that the pollen 
grains in the water sink down to the stigmas underneath 
the surface. 
Summary. 
1. The male flowers differ from those of Vallisneria — 
except as regards the perianth — in that the filaments are 
scarcely developed and the anthers are directed straight 
upwards. 
2. The pollen-grains are very large—about 170 ^ in 
diameter — and are heavier than sea-water, owing to the 
presence of numerous starch-grains. 
3. The pollen-grains have only a single smooth wall, 
probably the exine. 
I 8(10)04 (21) 
