122 SUMMER FLOWERS. 



tween the two species found in this country, the chief points 

 of dissimilarity being the slightly smaller size, the narrower 

 leaves, and the slightly interrupted flower- spike. 



The Ivy-leaved Duckweed"^ is a curious little plant, coming 

 in the same category as the last. The group of Duckweeds 

 consists of singular aquatic plants, resembling little green 

 scales floating on the surface of stagnant waters, and forming 

 part of the Pistiaceous, or, as Mr. Bentham calls it, Lemna- 

 ceous family. They are but rarely met with in flower, and 

 the flowers are so small and simple, that even when present 

 they are not readily detected. The Ivy-leaved species repre- 

 sented in our plate, 'has, it will be seen, no distinct stem or 

 leaves, but consists of small, leaf- like fronds, of a lance-shaped 

 figure, minutely toothed at one end, and tapering to a stalk- 

 like base at the other. Usually two young fronds grow from 

 opposite sides of the older one near its base, each one producing 

 eventually a single root from beneath. In this way growth goes 

 on, the fronds becoming detached, and themselves producing 

 others from their sides. The roots, which strike down per- 

 pendicularly, are in all the species capped by a small calyptra, 

 or sheath. They increase " not only by seeds, but more abun- 

 dantly by buds concealed in the lateral clefts of the parent 

 frond, which growing out on two opposite sides into new 

 plants, and these again producing offspring in the same way, 

 while still attached to their parents, present a most curious 

 appearance. ^^ The minute flowers grow from a fissure in the 

 edge of the frond, two together, the inflorescence consisting 

 of a membranaceous bract or spathe enclosing two stamens, 

 and a single one-celled ovary^ both without trace of a perianth. 

 Dr. Lindley describes this structure as follows : — the flowers 

 are two in number, one male and the other female, lying 



* Lemna trisulca — Plate 21 E. 



