THE ARROW-HEAD— continued. 
Other leaves float on the surface and have an ovate or heart-shaped blade ; while 
the majority of the leaves are generally the more distinctively arrow-shaped ones 
which rise erect above the water. These are from two to eight inches long in the 
blade, the barbs being about half of this, and the stout, spongy, three-sided leaf-stalks 
varying from eight to eighteen inches or more in length, according to the depth of 
water from which they rise. The veining of these elegant glossy leaves is, it will 
be noticed, of a simpler type than that of the somewhat similarly shaped leaves 
of the Lords-and-ladies ( Arum maculatum L.). The veins here are of but two 
degrees of coarseness and these sharply contrasted, the stout longitudinal ones 
converging towards the base and apex of the leaf, some of which bend round into 
the barbs or auricles , and the much finer obliquely transverse nervures ; whereas 
the Arum approximates to the Dicotyledons in the gradually diminishing coarseness 
of the veins at each branching, producing a network of far more irregular appearance. 
It will be readily understood that the variation of leaf-form with the surrounding 
conditions has given rise to the description of several so-called varieties. 
The flower-stalk is similar to the leaf-stalk in texture and rises unbranched 
slightly above the level of the water, so that it too is from eight to eighteen inches 
or more in height. It bears from three to five whorls of blossoms, some little 
distance apart, with from three to five flowers in each whorl, the lower whorl being 
carpellate and having shorter flower-stalks, and those in the upper whorls more 
numerous, with slightly longer stalks, and staminate. The flowers are about half 
an inch across, but the upper (staminate) ones are larger than the lower (carpellate). 
The three ovate concave green leaves of the calyx persist in the fruit stage ; but, as 
is generally the case among the Alismace <£, the large and conspicuous petals fall off 
early. They are three times as large as the sepals, rounded and white, and 
gradually spread out from a concave to a perfectly flat condition ; but their short 
claws or pointed bases are beautifully tinged with lilac. 
The heart-shaped anthers of the stamens in the upper flowers are also of a violet 
colour, and the number of stamens, which is about twenty-four, lends some support 
to the opinion that the flowers are only visited by flies for the sake of the pollen 
and do not produce nectar. At the same time, the mere separation of stamens and 
carpels in distinct flowers making self-pollination impossible would necessitate the 
production of more pollen, much being inevitably wasted. 
The carpels are also numerous, and, though compressed, form a head and not a 
ring as do those of Alisma. They are indehiscent and one-seeded, but swell out on 
their outer margins into a spongy wing containing a good deal of air and acting 
apparently as a float ; whilst the polished seeds are not wetted by water, another 
character which probably aids in their dispersal. 
The earliest record we have of this plant was from the Tower ditch, and not a 
hundred years have passed since it was growing not only in the ditches of Battersea 
Fields but even in the Thames itself near the Temple stairs. 
