3G ON THE HIBERNATION OF LEMNACE^. 



from N. Bulbocodium by its slender tube, biseriate stamens, long pedi- 

 cels, and reflexed divisions ; and from N. triandrns, which otherwise it 

 very closely resembles, by its longer corona. We have seen wild spe- 

 cimens only from the Isle of Glenans, in Brittany, gathered by Gay 

 and others ; and from Portugal, gathered by Baron Paiva, and are not 

 aware that it is now in cultivation in this country. We follow Redoute 

 and De CandoUe in regarding it as the CalatJiuius of Linnaeus, but the 

 plant figured in the ' Botanical Magazine ' under that name is very 

 different, being a slight form of N. odortis. 



(To be coHtinued.J 



ON THE HIBERNATION OF LEMNACE^. 

 By F. Van Horen. 



Abridged and Translated from the Bulletin de la Societe Roi/ale de Botanique 

 de Belgiqxie for Aug. 1869, by Alfred W. Bennett, M.A., B.Sc, F.L.S. 



Notwithstanding the attention paid to the physiology of the Lem- 

 nacece by Richard, Brongniart, Schleiden, Hoffmann, Weddell, and other 

 botanists, and the magnificent monograph of the Order by Hegelmaier, 

 M, Van Horen has recently afresh investigated some points in their 

 physiology, especially those connected with the phenomena of hiberna- 

 tion, and has arrived at conclusions in some respects difierent from 

 those of previous observers. The Order is represented in Belgium by 

 the same five species as are found in England, which, however, follow- 

 ing other Continental botanists, M. Van Horen divides into two sub- 

 orders, Lemnece and Wolffctp, and four distinct genera : — Leunia minor 

 and gihba, Spirodela polt/rrhlza, Stanrogetoii trisulca, and JFoIffia 

 arrliiza. 



The whole tribe of Lemnas possesses an apparatus of air-vessels, 

 consisting of lacun?e and passages. The petioles and roots contain 

 elongated tubular anastomosing passages; in the leaf itself the cham- 

 bers are of a considerable size, and one situated immediately beneath the 

 epidermis. The submerged leaves of aS". trisulca contain no lacunae, as 

 they have no stomata ; in L. gibha and minor, and S. 'polyrrldza, they 

 are spread over almost the whole surface of the leaf; in S. trisulca they 

 are more unequally distributed. 



