3$ 



6 



Of Vegetation. 





inconvenience we may obferve, that nature 

 has provided feverai Diaphragms, befides 

 thofc at each knot, which are placed at 

 fmall diftances acrofs the pith ; thereby pre- 

 venting its too great lateral dilatation. Thefe 

 are very plain to be feen in Walnut-tree 

 fhoots ; and the fame we may obferve in the 

 pith of the branches of the fun-flower, and 

 of feverai other plants 5 where tho' thefe Dia- 

 phragms are not to be diftinguifhed while the 

 pith is full and replete with moifture, yet 

 when it drys up, they are often plain to be 

 feen ; and it is further obferved, that where 

 the pith confiftsof diltinft veficles, the fibres 

 of thofc veficles are often found to run 

 horizontally, whereby they can the better 

 refill the too great lateral dilatation of the 

 fhoot. 



We may obferve that nature makes ufe of 



the fame artifice, in the growth of the feathers 



of Birds, which is very vifible in the great 



pinion feathers of the wing, the fmaller and 



upper part of which is extended by a fpongy 



pith, but the lower and bigger quill part, by 



a fcrics of large veficles, which when replete 



with dilating moifturc do extend the quill, 



but when the quill is full grown, thefe 



, veficles 



