CLASS II. ORDER I. 



LEMNA. 31 



the English name, Duckireed. — We find a variety of this species in 

 the pools about Sheffield, with the fronds elliptical, ovate, larger, 

 thinner, slightly convex above, and of" a more compact texture, a much 

 paler colour, and slightly concave beneath. 



Habitat. — Stagnant waters, very common. 



Annual ; flowering in June and July. 



These minute plants, called Water-fens, Duchneat, or Duckweed ^ 

 although frequently looked upon with disgust, and reviled with great 

 acrimony, are nevertheless of vast utility, particularly in covering the 

 surface of water, which becomes, during a great pai-t of the summer, a 

 depository for the lar\fe of insects, to an extent almost incredible, and 

 thus affording an abundant supply of food for fish. They are of the 

 greatest utility in covering, wholly or partially, the surface of preserve 

 ponds for carp and tench, in which we have observed the fish increase and 

 thrive with great rapidity, while in those ponds which are exposed, and 

 in which neither plants nor insects are allowed to accumulate, and 

 consequently the supply of food scanty, the fish do not either in- 

 crease to that extent, nor are they in that condition, as in the fonner 

 case. This, how ever, is not their only utility : — there is no doubt but 

 the layer of vegetating matter, which they form on the surface of 

 stagnant water and pools, is a great means of purifying it of much of 

 the noxious efiiuvia which emanates from the decaying matter accu- 

 mulated in such situations. We thus perceive, even in these appa- 

 rently insignificant weeds, the incontrovertible evidence that nothing 

 has been made in vain . 



The research and investigation of scientific botanists have of late 

 unveiled many of the .secrets of nature, and some of the recent and 

 most valuable discoveries are associated with the names of the noblest 

 benefactors of our age. But in this most interesting, yet intricate and 

 difficult branch of Natural History — Vegetable Physiology, there is 

 yet a vast field to explore, and much remains to be done before the 

 opinions of even the most eminent physiologists can be reconciled. 

 The causes of irritation of plants have been speculated upon, and 

 some have attempted to account for this singular phenomenon by re- 

 ferring it to mechanical structure, while others have ascribed it to the 

 presence of a vital principle analagous to that of animals. To show 

 that the latter is most accordant with the sense in which we are accus- 

 tomed to view objects endowed with vitality and possessing spontaneous 

 motion, we might refer to the lower orders of the animal and vegetable 

 creation, and, by tracing either to their simplest form, descend till the 

 distinction is lost, and we find both united in the same individual. In 

 accordance with what has just been stated, the roots of the various spe- 

 cies of Lemna will be found interesting, and in some degree illustrative 

 of the preceding remarks. If a plant of Lemna, with a full-grown 

 root, be removed from the water, and held in an inverted position for a 

 few minutes in a dry atmosphere, the root being composed of a very 



