226 - Linnean Society. [December 17? 



important subject. He denies the descent of the sap, and asks, " Who 

 has met with sapless branches in winter, or surcharged roots at the 

 same season?" He states that "the spring movement of the sap 

 begins (and necessarily must begin) at the top of the tree, and its 

 fluxion is generated gradually downwards until the whole is in mo- 

 tion." It is by means of this descending fluidity, and not by any 

 descent of the sap itself, that he explains the callosities or swellings 

 observed above a ligature, on the upper edge of a wound, and in 

 various other circumstances. Instead of attributing the formation of 

 the tissues of the plant to the organizable property of the elaborated 

 sap, he believes that the membranes and every other organic part or 

 constituent of the plant have rudimental existence and identity before 

 development. He regards the cambium as the seat of vegetable life 

 and the origin of all vegetable growth. From this living body (which 

 lie calls the indusium or vital membrane) he believes that the axis of 

 wood is annually enlarged in diameter, and the bark is thickened ; 

 from this, and this only, buds and roots are produced ; and wounds 

 are healed by its gradual extension. The paper concludes by a 

 reference to the opinions of Bonnet, DeCandoUe, Mirbel, and Du- 

 trochet. 



December 17. 



R. Brown, Esq., V.P., in the Chair. 



Dr. Lankester, F.L.S., exhibited a specimen of an Agaric in which, 

 gills were developed on a portion of the surface of the pileus, directly 

 over the stipes, resulting apparently from an extension of the growth 

 of the stipes, and a rupture of the external membrane of the pileus, 

 throwing up the internal or gill-producing membrane. 



Read, " Additional Remarks on the Spongilla fluviatilis." By John 

 Hogg, Esq., M.A., F.R.S., F.L.S. &c. 



In this paper Mr. Hogg commences by claiming a priority to M . 

 Laurent in the discovery of the locomotive germ-like bodies of Spon- 

 gilla, and in comparing them with the spontaneously moving spo- 

 rules of Ectosperma clavata of Unger. In proof of this priority he 

 refers to his memoir, published in 1 840, in the eighteenth volume of 



