42 Bibliographical Notices, 



resin the author terms them Pearl glands, (Perldriisen) ; these occur 

 in Cecropia, Begonia, Piper, Bauhinia, Urtica, and many other phints. 

 Remarkable is the ascent Qiinantreten) of a spiral vessel up to the 

 gland in the marginal glands of Drosera ; in this case likewise the 

 cellular sap globules possess motion. The consideration of the nec- 

 taries, with some reference to Kurr's memoir on this subject, forms 

 the conclusion. The second section treats of the internal glands ; 

 they are described and figured from Dictamnus, Ruta, Melaleuca, 

 Citrus, Hypericum, Gossypinm, &c. The so-called glands of the 

 Labiatce are treated of in supplementary notes. The fourth chapter 

 relates to the secretion of peculiar substances by individual cells in 

 the interior of the cellular tissue. It is a well-known fact, observes 

 the author, that individual cells at times contain a colouring sub- 

 stance which the adjacent cells do not exhibit ; the formation of 

 chlorophylle must also be regarded as a product of secretion. In the 

 Lysimachi(E, it is in some single large cells that the red resinous 

 pigment is situated, which appears to be composed of a number of 

 minute bars (Stabchen). These resinous secretions are exceedingly 

 remarkable in the elongated cells of the parenchyma near the spiral 

 tubes in species of Aloe, where at first brown resinous globules 

 occur along with green globules, gradually increase in number, and 

 at last fill in a mass the entire cell. In the roots of the Valeriance 

 there are also found, in the outer layers, resinous globules in the 

 cells ; a similar occurrence is also described in Amomum, Curcuma, 

 and other Scitaminece. The fifth chapter is devoted to the consi- 

 deration of the vital sap or milksap vessels (^vasa laticis) ; the author 

 here endeavours to maintain and confirm his opinion that they pos- 

 sess walls, and are therefore true vessels ; he also endeavours to de- 

 monstrate the motion of the sap in them, although he is not able to 

 establish any result founded on direct observation respecting the 

 terminal extremities and the mode in which the current is carried 

 through the entire plant ; he lastly treats of the external structure of 

 the milk sap and its globules, as also of the chemical characters it 

 presents. The sixth chapter contains some concluding remarks ; the 

 author enlarges on the phsenomena in relation to which substances 

 are secreted externally without the existence of any peculiar appa- 

 ratus ; as in the scales of buds, in the aerial roots of Mais, in the 

 occurrence of tragacanth, in the efflorescence of sugar on Algce, of 

 waxy substances on fruits and leaves, &c. In this memoir, which 

 contains so great and valuable a mass of information, we are glad 

 to find that the author does not give way to a polemical spirit. — 

 IJniuca, Part 111. 1839. 



