SCIENCE-GOSSIP, 



[Jan. 1, 1865. 



Sucli students of Botany as may be willing 

 to devote time and attention to these small 

 plants, will find that there is much to be 

 learnt respecting them. One species, the 

 Greater Duckweed, has never been seen in 

 flower in this country ; and two others, the 

 Ivy-leaved and Gibbous Duckweeds, flower 

 but rarely, whilst the fourth, or Lesser Duck- 

 weed, is more often met with in flower than 

 any other species ; but if we may judge from 

 our own experience, this occurs only under 

 rare and exceptional conditions. This ex- 

 treme rarity in flowering has compelled us to 

 go to other sources than nature herself for 

 details of the floral organs, to meet with 

 more or less imperfection or dissatisfaction. 



Yig. 3. Greater Duckweed {Lemna polyrrJdzd) . 

 Eig. 4. Gibbous Duckweed {Lemna gibba). 



This is true to such an extent of the Greater 

 Duckweed, that we have been compelled to 

 adopt, probably the only drawings in exist- 

 ence of the flowers of this particular species, 

 made in the first instance by poor artists from 

 very indifferent sketches, but we must take 

 such as we can get and "be thankful," 



These four species are to be found, more or 

 less abundantly, in this country, and the resi- 

 dent in London has the advantage of being- 

 able to find them all in plenty, without going 

 out of sight of town. There is at least one 

 other species, to which we have not alluded, 

 closely resembling the Lesser Duckweed, 

 which may yet be found in Britain, though 

 its occurrence has not at present been recoi*ded. 



Eis'. 5. Flower of Ivy-leaved Duckweed {Lemna 



trhulca), from Sowerby. 

 Eig'. 6. Details of fruit of tlie same, from Nees 



von Eseubcck's " Genera Plantar urn." 



The Ivy-leaved Duckweed has fronds of a 

 very different shape from those of the other 



species, and thinner. They are nearly half 

 an inch in length, not quite half as broad, 

 narrowed towards one end, and attenuated 

 into a little stalk at the other, with a single 

 fibre produced from the under surface. This 

 also occurs plentifully in all the ditches in the 

 neighbourhood of Tottenham, and elsewhere. 

 The Greater Duckweed ha?) fronds larger 

 than in any other species, nearly circular, 

 rather thick, and with a clustei" of fibres pro- 

 ceeding from the under-surface of each frond. 

 Though said to be rare, it grows in abundance 

 in the Hampstead Ponds, and in all the 

 ditches and still waters bordering the Lea at 

 Tottenham, and the surrounding district. 



Eigs. 7, 8. Details of flower and fruit of Lesser Duck- 

 weed {Lemna minor), from Nees von Esenbcck. 



The Lesser (or common) Duckweed has 

 small ovate fronds, cohering three or four 

 together, with one fibre proceeding do wnv/ards 

 from the under surface of each, the ovary con- 

 tains but a single ovule j at least such is the 

 character given by those v/ho have examined 

 the fruit. Of coiirse, this species occurs in 

 still water everywhere. 



Eig. 9. Elower of Greater Duckweed {L. polyr- 

 rldza), from Reichenbach's " Elora Gernianica." 



Eig. 10. Elowers of the same species, from 

 Lamarck's Encyclopajdia. (\Fe know of no 

 figure of the fruit of this species.) 



The Gibbous Duckweed has fronds shaped 

 like those of the Common Duckweed, but 

 thicker and rather larger, flattened above, and 

 convex beneath. Each frond has a single 

 rootlet. The ovary is said to contain two, or 

 more, ovules. This species is probably not of 



