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XXXVIII. On the Beneficial Effects of the Accumulation of Sap 

 in Annual Plants. By Thomas Andrew Knight, Esq. F. R. S. 

 President. 



Read December 20, 1830. 



B iennial plants very obviously form in one season the sap, which 

 they expend in the following season in the production of blossoms 

 and seeds ; and the capacity of the reservoirs they form is greater, 

 or less, in proportion as external circumstances are more, or less, 

 favourable. Trees also (as I conceive myself to have satisfactorily 

 proved in the Philosophical Transactions) generate in a preceding 

 season, or seasons, the sap which feeds, in the spring, their unfolding 

 blossoms and young leaves. Annual plants, on the contrary, pos- 

 sess no such reservoirs ; and they must generate, in each season, all 

 the sap which they can expend, exclusively of the very small por- 

 tion derived from the seeds, from which they spring. But by 

 appropriate management, and creation of Varieties, Annual Plants 

 may be made to accumulate, in one period of their lives, the sap 

 which they expend in another, with very great advantages to the 

 cultivator. 



The first produced female blossoms of the Melon Plant, particu- 

 larly of the larger and superior varieties, do not often set; and if 

 they set, the fruit they afford never attains as large a size, or as 

 much excellence, as the same plants, at a more mature age, would 

 have given to it under the same external circumstances. This, I 

 imagine, arises not only from the different quantity, but from the 

 different qualities, of the sap in the young, and in the more mature, 

 plant ; for I have found the sap of very young Birch and Sycamore 

 trees to be specifically much lighter, and to contain much less 



