THE AMERICAN BOTANIST. 
13 
In some members of the order, notably in the arrow- 
heads and water-plantains there is a tendency to a 
multiplication of stamens and pistils but in the majority 
there is a definite number of these organs, usually six as 
to stamens and three as to pistils. In many of the plants 
there is also seen a tendency to surround the flower or 
flowers with a spathe. 
The order is remarkable for the variety and strange- 
ness of ways in which the flowers are pollinated. The 
showy flowers of the Alismaceas are pollinated by bees 
and other short-tongued insects. In Ahsma plantago, 
the water-plantain, according to Rendle, the fleshy ring 
formed by the base of the filaments excretes twelve drops 
of nectar. In the arrow-head (Sagittaria) the large and 
showy flowers are noticeable for appearing in whorls of 
three, the upper whorls containing only staminate 
flowers, the lower pistillate. In the pond weeds, although 
the flowers contain both pistils and stamens and are 
wind pollinated, there is considerable likelihood of cross- 
pollination since the stigmas ripen before the anthers. 
The eel-grass is famous from the fact that its pistillate 
flowers rise on long stems to the surface of the water, 
while the short-stemmed staminate flowers, in order to 
reach them break loose from the plant and rise to the 
surface, being helped thereto by a bubble or balloon of 
oxygen gas providently excreted before the journey 
begins. Still other members of the order have flowers 
always beneath the water and the pollen instead of being 
round, as is usual, is long and thread-like and of the same 
specific gravity as water. It, therefore,, neither rises to 
the surface nor sinks to the bottom, but swims about 
until caught upon the fringed stigmas. The seeds are 
usually, if not always, distributed by water. 
In addition to seeds many plants of this order have 
other methods of distribution. Runners which form 
tuber-like bodies capable of producing new plants are 
common in the eel-grass, the pond weeds and the arrow- 
heads. In the former the tips of the shoots in autumn 
becomes detached and sink to the bottom to give rise to 
