3 3 6 Of Vegetation. 



inconvenience \vc may obferve, that nature 

 has provided feveral Diaphragms, beftdes 

 thofe at each knot, which are placed at 

 fmall diftanccs acrofs the pith \ thereby pre- 

 venting its too great lateral dilatation. Thefe 

 are very plain to be ieen in Walnut-tree 

 fhoots 5 and the fame we may obferve in the 

 pith of the branches of the fun-flower, and 

 of feveral other plants ; where tho' thefe Dia- 

 phragms are not to be diftinguifhed while the 

 pith is full and replete with moifturc, yet 

 when it drys up, they are often plain to be 

 ieen ; and it is further obferved, that where 

 the pith confifts of diftincr, veficles, the fibres 

 of thofe veficles are often found to run 

 horizontally, whereby they can the better 

 refift 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 villble in the great 

 pinion feathers of the wing, the fmaller and 

 upper part of which is extended by a fpengy 

 pirn, but the lower and bigger quill part, by 

 a feries of large veficles, which when replete 

 with dilating moifture do extend the quill, 

 but when the quill is full grown, thefe 



veficles 



