SECT. II. ASCENT OF THE SAP. Ill 



far obtained, another inquiry remains yet to be in- 

 stituted. In passing through the channel of the Vessels 

 alburnum, does the sap ascend promiscuously by ^hklfit 

 the whole of the tubes composing it, or is it con- ascends 

 fined in its passage to any peculiar set ? 



The earliest conjectures recorded on this subject 

 are those of Grew and Malpighi, who, though they 

 maintained that the sap ascends chiefly by the 

 bark, did not yet deny that it ascends also partly 

 by the alburnum or wood : but their opinions do 

 not at all coincide with regard lo the peculiar set 

 of vessels through which the sap ascends the al- 

 burnum. Malpighi thought it ascended through According 

 the channel of the tubes formed by the woody ^Md- 

 fibre, which he describes under the appellation of P 5 S hi - 

 fistula Ugnecz ;* regarding the tracheae, which he 

 represents as constituting also part of the wood, 

 as being confined merely to the function of con- 

 ducting air. But Grew thought it ascended the 

 alburnum only through the channel of the tra- 

 cheae, -j~ which he represents as being numerous 

 both in the stem and root, and capable of conduct- 

 ing not only air but sap. Such were the primitive 

 conjectures entertained on this subject, at a time 

 when phytological inquiry was but yet in its in- 



* Sunt autem hae fistulce ejusdem naturae cum exaratis cor- 

 ticem compingentibus, et consimilcrn admittunt succum qui ex 

 natures legibus sursum pellitur. Anat. Plant, xi. 



t In the wood the sap ascendeth only by the air vessels. Yog, 

 of Trunks, chap. i. 



