i)ESCRII*TlON OF THE PIR*. fill 



Other part. The seeds are not only full of it, but are 

 covered without by bladders filled with the same juices. 



As I have now concluded my account of the firs, 1 shall Wood 

 finish with a few words respecting wood in general, as one of 

 the most important subjects in the botanical world. Some of 

 our best physiologists have made a strange mistake, if I may 

 venture to say so, in supposing it impossible that the wood capable of con- 

 can convey sap, because the wood can be torn to atoms* ^^^^"^^^P* 

 Look in the microscope; at one of these shreds, and it will 

 be found pointed, not a sap vessel, but a fragment. The 

 sap vessels are round, but the wood has besides the bastard 

 pipes, pieces of thin flimsy texture> which fill up all the 

 places between the sap vessels, and sire very large in young 

 wood, and will divide into hairs; which are often taken for 

 important vessels. The sap vessels also will separate, but 

 I cannot conceive their being thus flexible, and easily torn, 

 lessens their power of conveying sap when perfect and 

 whole. But is it not an easy thing to prove, that they art 

 the real sap vessels ? since they are the only pipes yet found 

 in plants, that will convey coloured infusions, as ail ac*- 

 knowledge. I have repeatedly taken a branch three or four 

 feet long, and though 1 could not make the coloured mix- 

 ture rise the whole space at once ; yet by cutting a little 

 below where it stopped, 1 have made it by degrees rise the 

 whole length, and thus proved, that there is no real stop- 

 page in the vessels ; but that the sap is capable of flowing 

 in one even current from the bottom to the top of the tree; 

 and the only reason we cannot make coloured liquids rise 

 with the same ease and quickness as the sap is, that our 

 mixtures are not so well tempered as Nature*s: there is al- 

 ways some dust, some matter to choak these little pipes. I 

 once made some very curious experiments on capillary at- 

 traction, in very diminutive glass pipes, wl^ich rendered thi;* 

 most evident, not only between the liquids, but between the 

 pipes which we make when compared to the perfect works 

 of Nature, 



As I cannot believe, that any one can strip off the bark Flower budj 

 of a tree, and yet be doubtful whether the flower buds ^^o''*/^® '°*^ 

 come from the interior of the wood, I am very anxious to 

 persuade the physiologiit to study at this seftson the tree 



P 2 ftewlr 



