ON THE LIMITS OF SINGLE VISION. 1<25 



sap, whicli bus been dei^Obited at rest (laiiug the autumn and 



winte)-, is again called into action to teed the buds, which 



eio,i;-»*.ue into parts of the stems of the futuve plants in the 



spring, tibrous roots are emitted from the the bases of these 



stems, whi'st buds ufe generated at the opposite extremities, 



as in the cases 1 have meutioued respectiug trees. 



Many naturalists* have supposed the fibrous roots of all Fibrous roots, 



plants to be oi' autiual duration only, and those of bulbous ^^.'^""''^"^ ^'"* 

 ^ , ' tuberous root- 



aud tuberous rooted plauto ieitaiuly are so; a» m ti.ese. lia- ed j;lants aa- 



ture has provided a distinct reservoir tor the sap which is to i^^^U 

 form the first leaves and tibrous roots of the succeeding sea- 

 son : but the organizatioii of trees is very different, and the of trees pere» 

 alburnum and bark of the roots and stems of these are the ""'* 

 reservoirs of their sap during the wiuterf. A\ hen, however, 

 the fibrous roots of trees are crowded together in a garden- 

 pot, they are often found iiieless in the succeeding spring; 

 but I have not observed the same mortality to occur in any 

 degree, in the -roots of trees when g-fowing, under favourable 

 circumstaiices, in their natural situation. 



I am prepared to olter some observations on the causes 

 which direct the roots of plants in search of proper nutri- 

 ment, and which occasion the root of the same plant to as- 

 sume dirterent forms under different circumstances; but I 

 propose to make these observations the subject of a future 

 communication. 



I am, my dear Sir, 



with great respect, 



your mud) obliged servant, 

 Elton, Dec. oo, \^QS. THOMAS AND. KNIGWT. 



IX. 



Inquiries into the Limits of Single Vision, and the correspond- 

 ing Points in the Retina, ^r,: bt/ Dr. Hald XT, Secretari/ 

 to the Academy of NancyX» 



JtN the paper on double vision, printed in this Journal for Correspondine 

 iiovember, 180611, 1 referred the singular phenomena there points on the 



retina, 

 * M, Mirbel's Traite d' Anatomic, &c. Dr. Smith's Introduction to 

 Botany. f Phil. Trans, for 1805. 



iJoum.de Physique,vol.LXV,p. 16. 1| See Journal, v«l, XVII, p. 201. 



recited 



