Miscellaneous. 155 



Having cut through the epidermal cells, so as to discharge their 

 contents, and thus prevent them from exerting any lateral pressure 

 on the guardian-cells, it was found that when placed in water (which 

 they imbibe), the guardian-cells increased the space between them 

 very perceptibly ; but when placed in a solution of sugar (into which 

 they exude a portion of their contents), they closed it completely. 

 By changing from water to a solution of sugar, the same opening 

 might be alternately opened and closed. Another series of experi- 

 ments on intact leaves showed that this action of the guardian-cells 

 is impeded by the pressure of the epidermal cells, in proportion as 

 they come into contact with the former. This is also shown by the 

 fact, that when this pressure is taken off by emptying the epidermal 

 cells of their contents (which may be done by immersing the latter 

 in a solution of sugar), the guardian-cells always open. As the epi- 

 dermal cells contain more sap than the guardian-cells, the same result 

 is obtained by letting a leaf wither off. The orifices of intact leaves 

 cut off in the morning were found to be closed ; when exposed to the 

 sun for several hours, they opened again, but closed with rapidity 

 when immersed in water, — showing that the power of the guardian- 

 cells is increased, in comparison with that of the epidermal cells, by 

 the influence of light and heat, quite independently of the humid state 

 in which they may occur. This, the author thinks, can hardly be 

 explained except by assuming that when the guardian-cells are ex- 

 posed to the influence of these agents, they form such combinations 

 as are able to induce a powerful endosmosis, and are more or less 

 decomposed when light is withdrawn ; for, as is well known, the 

 guardian-cells, like the cells of the parenchyma, contain chlorophyl- 

 laceous matter. 



Direct comparative measurements show that the projecting part of 

 the guardian-cells, beyond the anterior cavity, contracts but slightly, 

 so that the process is effected chiefly by the change in the form of 

 the boundaries of the true opening. 



The guardian-cells expand most in a vertical direction, and thus 

 change their transverse diameter from a circular to an elliptical form, 

 so as to draw in the thinner portion of the lateral surface which lies 

 free in the opening of the stomate. This explains why the opening 

 is not closed when these cells are distended by the water which fills 

 them. — Botanische Zeitungy 1856, No. 40, and Silliman's Journal, 

 March 1857. 



Descriptions of new Norwegian Annelides. By M. Sars. 



Family Telethusa. 



Genus Notomastus, Sars, n. g. 



Lobus capitalis conico-acuminatus. Os subtus ; pharynx exsertilis 

 breviter clavata, papilhs obsita. Anterior corporis pars cylindrico- 

 subfusiformis, e segmentis duodecim medio sulco in annulos duos 

 divisis, primo absque et cseteris undecim utrinque fasciculis binis 

 setarum capillarium, mamillis pedalibus carentibus, composita. Pos- 

 terior corporis pars longior et tenuior, e segmentis constans numerosis 



