VEGETATION OF SEEDS. 409 



The first column of this Table gives the supposed proportion 

 of alloy in 100 parts of the respective coin ; the second gives 

 the weight of silver contained in each coin, on the supposition 

 that the weight of the copper with which the silver is alloyed is 

 always 1. 



vir. 



On the Direction of the Radicle and Germen during the Vege- 

 tationof Seeds. By Thomas Andrew Knight, E^q. 

 F.R.S. In a Letter to the Right Hon. Sir Joseph Banks, 

 P.R.S.* 



My dear Sir, 



I 



T can scarcely have escaped the notice of the most inatten- Vertical posi- 

 tive observer of vegetation, that in whatever position a seed is y^ggtables 

 placed to germinate, its radicle invariably makes an effort to gi"ow, 

 descend towards the centre of the earth, whilst the elongated ger- 

 men takes a precisely opposite direction : and it has been proved 

 by Du Hamel,* that if a seed during its germination, be fre- 

 quently inverted, the points both of the radicle and germen 

 will return to the first direction. Some naturahsts have sup- 

 posed these opposite effects to be produced by gravitation : and — ascribed t© 

 it is not difficult to conceive that the same agent, by operating 

 on bodies so differently organized as the radicle and germen of 

 plants are, may occasion the one to descend and the other to 

 ascend. 



The hypothesis of these naturalists does not, however, appear Not yet prov.^ 



ed by facts, 

 to have been much strengthened by any facts they were able to 



adduce in support of it, nor much weakened by the arguments 

 of their opponents ; and, therefore, as the phenomena observ- 

 able during the conversion of a seed into a plant are amongst 

 the most interesting that occur in vegetation, I commenced the 

 experiments, an account of which I have now the honour to 

 request you to lay before the Royal Society, 



* Philos. Trans. 1806. f Physique des Arbres. 



Vol. XIV. Supplement. Ggg descent 



