SECT. II. ASCENT OF THE SAP. 121 



this can refer only to their uncoiled state, in which 

 they do not form a tube, but merely a loosely spiral 

 line ; for in the coiled up state in which they 

 exist in the living vegetable and in which the spires 

 are united, they form a perfect tube, which we 

 cannot regard as incapable of transmitting moisture 

 without some proof. On the contrary it seems to 

 have been ascertained that they do contain mois- 

 ture. Hedwig, who examined with great care, and 

 with a view to the very point in question, the stem 

 of the Cucurbita Pcpo, and Momordlca Elate- 

 rium, in which the spiral tubes are comparatively 

 large, affirms that the juices may be seen issuing 

 from their orifices, if the horizontal section is in- 

 spected immediately after the stem is divided.* 

 Senebier gives a similar account of their appearance 

 in the stem of the Sagus farimfera, which he 

 had chosen for the subject of his observations.-}- 

 And Hedwig appears to have succeeded even in 

 inspecting them by means of steeping a portion of 

 the stem in coloured infusions ; and also in mea- 

 suring their diameter, which he estimates at about 

 the -s-j-g- of a line. In these observations there 

 may certainly have been error; but from the known 

 accuracy of the observers we are warranted in re- 

 garding them as correct ; and consequently in con- 

 cluding that the tracheae or spiral tubes, where they 

 exist, do also conduct sap. 



But still there remains a question to be asked 

 * Fund. Hist. Nat. Muse. p. 55. f Pfys. Veg, vol. i. p. 107. 



