CLXXXII. — 1 THE COMMON MARE’S-TAIE. 
Hippuris vulgaris Linne. 
A S is commonly the case with aquatic plants, the vegetative structures of the 
Haloragidace# are in many of its species so specially adapted to the 
environment, and the floral organs are of so reduced a character, that it is not easy 
to determine the nearest affinities of the Family. Although Bentham and Hooker 
considered the valvate calyx and inferior ovary but slight indications of relationship 
to the Onagrace# , and preferred to place the Mare’s-tail Family in the Order Rosales , 
Eichler, Warming, and Engler all agree in placing it among the Myrtiflor# and in 
considering it undoubtedly a series of reduced forms related to Onagrace#. 
A small Family of less than a hundred species, the Haloragidace# , as again is 
frequently the case with aquatic plants, are practically cosmopolitan, though better 
represented in the South Temperate Zone than elsewhere. Most of them are 
herbaceous and live either in or near water. Haloragis , the largest genus, comprising 
as it does some fifty species, is mainly Australasian, and consists of large herbaceous 
plants living in damp situations ; whilst several South American species of Gunnera , 
though equally herbaceous, have enormous Rhubarb-like leaves several feet across 
which make them most valuable as ornamental plants by the water-side. The two 
genera which are represented in Europe are Myriophyllum and Hippuris. The 
Water-Milfoils ( Myriophyllum ) are so called, from the Greek /iupfos, murios, 
innumerable, <J>vWov, phullon , a leaf, and from the Latin mille, a thousand, folium , 
a leaf, on account of their finely-divided submerged leaves. Their inflorescences 
rise above water and the pollen of their small inconspicuous blossoms is carried by 
wind. From one species of this genus which abounds in the waters of Lake Titicaca 
on the confines of Bolivia and Peru, at an altitude of over 12,000 feet, the Indians 
construct rafts and sails ; but there are very few useful purposes to which any of the 
Haloragidace # are applied. The flowers of Myriophyllum , like those of Haloragis , 
may be complete and perfect, with four sepals, four petals, two, four, or eight 
stamens, and four carpels ; but the petals are sometimes absent and the flowers are 
often monoecious. Hippuris is, perhaps, monotypic, plants from the various distant 
regions in which it is represented, such as Australia and Fuegia, presenting no 
constant differences from our British species, H. vulgaris Linne. With its superior 
calyx represented by two rudimentary sepals, with no petals, one stamen, and one 
carpel, its flower is obviously much more reduced from the type of the Onagrace# 
than the tetramerous Myriophyllum or the dimerous Circ#a. 
The Family Haloragidace # as a whole may be characterised as aquatic or semi- 
aquatic herbs, with exstipulate and generally whorled leaves, inconspicuous flowers, 
often apetalous or monoecious, tetramerous, dimerous, or still further reduced, with 
a superior calyx, an indehiscent, inferior, capsular fruit, and one seed in each of its 
one to four carpels. 
