THE PRINCIPLES OF BOTANY. 
413 
The Frogbit — sometimes called the Pride of the Water — 
well deserves the latter appellation, as from its circle of float- 
ing uniform leaves the lovely silvery chalice of three-petalled 
flowers are pleasingly conspicuous. This also used to grow 
in the ponds and brooks of Battersea Fields, but it is not 
uncommon in wet marshy districts, especially near rivers, as 
in parts of Gloucestershire and Worcestershire near the hanks 
of the Severn. 
This is a very interesting plant for the fresh-water aquarium. 
The foreign plants of the order are also interesting, so 
much so that we must not omit to mention the Yallisneria 
and the Water- thyme. 
The first of these, Vallisneria spiralis , is remarkable for 
the curious arrangements which it possesses for bringing 
about fertilisation. This plant, as described by Professor 
Lindley, is one “ whose inflorescence lives and passes through 
all the stages of its existence under water, except just at the 
time when fertilisation is necessary, when the flowers rise 
above the surface for a few hours. Darwin, in his ( Loves of 
the Plants, 5 alludes to it in the. following strain, which, as 
well as the note upon this part of the poem, we transcribe 
for the information it is meant to convey : — 
“ As dash the waves on India’s breezy strand, 
Her hushed cheek pressed upon her lily hand, 
Vallisner sits, upturns her tearful eyes, 
Calls her lost lover, and upbraids the skies ; 
For him she breathes the silent sigh forlorn, 
Each setting day ; for him each rising morn.” 
“ This extraordinary plant,” as explained by our author, “ is of the class 
Two-houses. It is found in the East Indies, in Norway, and various parts 
of Italy. — Lin. Spec. Plant. They have their roots at the bottom of the 
Rhone. The flowers of the female plant float on the surface of the water, 
and are furnished with an elastic spiral stalk, which extends or contracts as 
the water rises and falls. This rise or fall, from the rapid descent of the 
river, and the mountain torrents which flow into it, often amounts to many 
feet in a few hours. The flowers of the male plant are produced under 
water, and as soon as their farina, or dust (pollen) is mature, they detach 
themselves from the plant and rise to the surface, continue to flourish, and 
are wafted by the air or borne by the currents to the female flowers.” — 
Darwin’s ‘Loves of the Plants, with Philosophical Notes,’ p. 33. 
This plant is kept by the microscopist for exhibiting the 
circulation of the sap in the tissue of the leaves. It is no 
less useful as a purifying adjunct in the freshwater aquarium. 
The Water-Thyme, named — 
Elodia Canadensis , Michaux ; 
TJdora Canadensis , Nuttall; 
Anacharis Alsinastrum , Babington ; 
Serpicula verticellata , Muhlenberg — 
