Jax. 1, 1865,J 



SCIENCE-GOSSIP. 



point out the features whereby the venomous 

 may be distinguished from the harmless 

 species, the CT^^er from the snake, it will be 

 well, in conclusion, to repeat what we have 

 advanced on this subject, in as concise a 

 manner as possible. 



It is the snake that is harmless, and the 

 re^;er that is venomous ; the latter being in- 

 nocuous also in winter, and most dangerous 

 in the hottest weather. The snake is com- 

 monly the lai'ger of the two, and is found in 

 the dampest situations, generally in near 

 jiroximity 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 some- 

 thing 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 vijoer to make an experimental 

 dart at their shins. 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. 



DUCKWEEDS. 



UPWARDS 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 Plistory. The Grecian 

 sage to whom we refer was Theophrastus, 

 who wrote a treatise on plants somewhere 

 about B.C. 300. This same Greek was ac- 

 quainted with a certain aquatic plant, 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 



* Lemna itself was probably suggested to Theo- 

 phrastus by the little island of Lemnos, in the 

 yEgeau sea, apparently lloathig on the water (to 

 compare large things with small), like the leaf of a 

 water-plant. 



enough to float a mimic boat in a mud-puddle, 

 as " duckweed." 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 difler 

 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 vege- 

 tating and sailing like little boats on the face 

 of the water. There are no real stems, and 

 no real leaves, but the whole plant 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 

 si^e 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 j 

 that are mature. The flowers, which are very j 

 simple, and equally rare, are produced from 

 cracks or fissures in the edges of the fronds. 

 These flowers consist of a little bract en- 

 closing two stamens and a small ovary. In 

 these points all the four species which inhabit 

 this country agree. 



To render our i-emarks on these species 

 more comprehensible we have given figures, 



Fig. 1. Ivy-leaved Duckweed {Lemna trisidca) 

 Fig. 2. Lesser Duckweed {Lemna minor). 



of which the first four represent the plants 

 in their actual size, i.e., The Ivy-leaved Duck- 

 weed {Lemna trisvJca), the Lesser Duckweed 

 {Lemna minor), the Greater Duckweed 

 {Lemna folyrrliiza), and the Gibbous Duck- 

 weed {Lemna gibba). 



