288 



Report of the Botanical Proceedings of the British Association for 



the Advancement of Science.* 



' On the Theory of the Formation of Wood and the Descent of the 

 Sap in Plants ; by Dr. Lankester.' The author drew attention to the 

 theory of the formation of wood in plants, and objected to the view 

 that the leaves form the wood, on the ground that the ligneous, like 

 all other tissues, were the result of the growth of cells which were not 

 formed in the leaves, but in all parts of tlfp plant. Wood was formed 

 in all parts of the plant where elongated cells where generated, quite 

 independently of leaves, or the formation of leaves : — as in the lower 

 part of the cut wounds of the stems of plants, in the portions of trunks 

 left when trees were cut down, in the abortive branches formed in the 

 bark of such trees as the elm and the cedar, and in other parts of the 

 vegetable structure. He also objected to the theory of the formation 

 of the ligneous or any other secretion, which might be subsequently 

 appropriated by the ceils, in the leaves alone. He maintained that 

 all the facts brought forward to support the theory of the descent of 

 the sap, might be explained on the known fact of the ready permea- 

 bility of the tissues of the plant. He related the details of experi- 

 ments performed on the species of Spurge ; in which the fluid was 

 found to exude from the stem and branches in these plants, just in 

 proportion to the quantity of fluid contained in the plant above or 

 below the section made. The cells of plants were nourished in two 

 ways: — first, by the sap containing carbonic acid, ammonia, and 

 other substances, — and secondly, by materials, as sugar, gum, &c., 

 formed in the cells. These latter were not formed solely in the leaves, 

 but in all cells. He regarded the leaves as organs by which the water 

 of the sap was got rid of, and by this means a further supply of sap 

 from the earth and atmosphere was insured. This function was per- 

 formed in subservience to changes which were attributed to a specific 

 vitality. 



Prof. Henslow said that he agreed with the views of Dr. Lankester 

 with regard to the theory of the formation of wood proposed by Du 



* Extracted from the ' Botanical Gazette.' This report, the only one I have seen 

 confined to the science of botany, has been drawn up with great care, and is probably 

 from the pen of the editor of the ' Botanical Gazette,' who was a member of the Com- 

 mittee for section D, which comprized Natural History, including physiology. A 

 lengthened report of the entire proceedings will be found in consecutive numbers of 

 the ' Athenaeum.' — Ed. 



