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] point out the features whereby the venomous may be distinguished from the harmless species, the viper from the snake, it will be well, in conclusion, to repeat what we have advanced on this subject, in a concise a manner as possible.

It is the snake that is harmless, and the viper that is venomous; the latter being innocuous also in winter, and most dangerous in the hottest weather. The snake is commonly the larger of the two, and is found in the dampest situations, generally in near proximity to water, in which it delights to bask. The snake has large plates, or scales, upon its head, few in number; in the viper they are numerous and small. The snake has no continuous line of a darker colour running along its body, but is spotted all over; the viper has a continuous line, zigzag and blotched, running down its entire length. The head in the snake is more depressed and acutely pointed in front than in the viper, which latter has a characteristic blotch something like the "death's head and thigh-bones" of the "death's-head moth," on the top of its cranium. Whether or not its venom is fatal, we would strongly advise our readers not to permit the viper to make an experimental dart at their skins. It is better to indulge in a shudder when only a harmless snake crosses our path, than make the mistake of hugging a viper to our bosom.

PWARDS of two thousand years ago, there flourished in Greece a certain philosopher, who, like Pliny and Aristotle, devoted a portion of his time and talent to the study of Natural History. The Grecian sage to whom we refer was Theophrastus, who wrote a treatise on plants somewhere about B.C. 300. This same Greek was acquainted with a certain aquatic lant, to which he gave the name of Lemna; but what the precise plant was to which he gave that name is now uncertain; it might have been a "duckweed," and it might have been something else. In more recent times this name has been adopted for a group, or genus, of aquatic plants, known to every child, old enouh to float a mimic boat in a mud-puddle, as "duckwood." It is to these plants—small, insignificant, and uninteresting, as they appear to be—that we propose adverting, with the view of pointing out wherein they differ from each other. Because, though many, perhaps, never looked at them with sufficient care or interest to recognise more than one form, others have detected variations to such an extent that they are enabled to point out three or four types, with distinct features of their own. Some may learn for the first time that four species of "duckweed" are found in Britain, others, cognizant of this fact, may wish to know more about them. In the first place, let us see in what points they all agree, or, as botanists would say, let us make out their generic character. All are floating plants, in no way attached to the soil, like the majority of plants, but vegetating and sailing like little boats on the face of the water. There are no real stems, and no real leaves, but the whole plants consists of little green fronds which look like leaves, and which are either separate, one from another, or cohere two or three together. One, two, or more little threads hang down from the under side of these fronds into the water, after the manner of rootlets, but they do not attach themselves. These fronds are multiplied by young ones growing out of the edges of those that are mature. The flowers, which are very simple, and equally rare, are produced from cracks or fissures in the edges of the fronds. These flowers consist of a little bract enclosing two stamens and a small ovary. In these points all the four species which inhabit this country agree.

To render our remarks on these species more comprehensible we have given figures,

Fig 1. Ivy-leaved Duckweed (Lemna triscula) Fig 2. Lesser Duckweed (Lemna minor).

of which the first four represent the plants in their actual size, i.e., the Ivy-leaved Duckweed (Lemna trisulca), the Lesser Duckweed (Lemna minor), the Greater Duckweed (Lemna polyrrhiza), and the Gibbous Duckweed (Lemnaa gibba).