The Air-vesicles of Bladderworts. 207 



THE AIB-VESICLES OF BLADDEEWOETS 

 (UTEICULAEIA). 



BT J. B. SCHNETZLEE. 



[In England we have, amongst our wild flowers, three Bladder- 

 worts — Utricularia vulgaris, or Bladderwort, growing in stag- 

 nant water; U. intermedia, a rare plant; and U. minor, or 

 lesser Bladderwort ; and many of our readers will be glad to 

 repeat the observations contained in the following paper, which 

 is translated from the " Archives des Sciences."] 



The genus Utricularia, or Bladderworts, comprises aquatic 

 plants found in the stagnant water of ditches, marshes, etc. 

 The leaves are submerged, and divided into fine threads, fur- 

 nished with vesicles, or utricles (asci), to which De Oandolle 

 ascribes the following characters : — 



These utricles are rounded, and furnished with a species of 

 movable operculum, or lid. In the youth of the plant, they 

 are full of mucus heavier than water, and the plant, weighed 

 down by them, remains at the bottom. Towards the season of 

 flowering, the leaves secrete a gas which enters the utricle, and 

 drives out the mucus, opening the lid for its escape. The 

 plant is thus supplied with a quantity of air-vessels, which 

 elevate it gradually, and cause it to float on the surface. The 

 process of flowering takes place in the free air ; and when it is 

 finished, the leaves again secrete mucus, which replaces the 

 air in the utricles, weigh down the plant, and cause it to 

 descend again to the bottom of the water, where it ripens its 

 seed in the situation in which they should be sown.* 



In spite of the labours of Gr6ppert,f Benjamin, J Schleiden,§ 

 Schacht,[j Eeinsch,^[ there is not yet a complete agreement of 

 botanists as to the origin and morphological signification of 

 these aerial vesicles. Before the publication of the works 

 cited, they were usually regarded as a modification of the 

 parenchyma of the leaves, which follows the numerous ramifi- 

 cations of the veins, under the form of a narrow band, and 

 which by dilating from time to time produced the utricles. 



Schleiden, who studied the development of these little 

 organs, saw them appear at the angles of the division of the 

 leaf under the form of little bodies like horns (cornets), sup- 

 ported on short pedicels. The lower side of the horn, and the 



* De Candolle, " Physiologie Vegetale," t. xi., p. 87. 



t " Botanisclie Zeitung," 1847, p. 721. % Ibid., 1848, p. 17. 



§ " G-rundziige der Wissenschaft, Botanik," 388, iv. Auff. 



|[ " Beitrage zur Anatomie," etc. 



IT "Denkslinflen der K. Bair. Bot. aesettschoft," 1859, B. iv. 153. 



