94 VITT.E CRYPTS. [BOOK T. 



which are the clavate vessels of oil found in the coat of the 

 fruit of Umbellifers, and which are commonly called vitt&. 

 Although the receptacles of secretion have no proper coat, 

 yet they are so surrounded by cellular tissue, that a lining or 

 wall is formed, of perfect regularity and symmetry. The 

 tissue of this lining is generally much smaller than that of 

 the neighbouring parts. When filled with a fluid having a 

 different refractive power from that of the surrounding parts, 

 these receptacles give a semitransparent dotted appearance to 

 the organs in which they occur, as may be seen by holding 

 up the leaf of an orange tree against the light. 



While, however, many kinds of receptacles of secretion are 

 mere cavities in the tissue, others are little nuclei of cells, as 

 in the Dictamnus (fig. 10. c.) These are of the nature of 

 glands, and are called internal glands by Meyen. 



Numerous modifications of these parts have been described 

 by German anatomists, especially by the last-mentioned author, 

 but they only relate to the refinements of the subject. In 

 figure, the receptacles are extremely variable, most commonly 

 round, as in the leaves of the Orange and of all Myrtleblooms 



thus of the Turpentine Vessels, or Gum Vessels, and what he called Lymphceducts, 

 or woody tissue of the liber : 



" Those in the Barque of Pine are likewise of two kinds. The inmost are 

 Lymphseducts, as in the two former. The utmost are not Milk- Vessels, but 

 Gum- Vessels, or Resiniferous : which stand straggling, and singly, about the 

 middle of the Barque. Out of these vessels all the clear turpentine, that drops 

 from the tree, doth issue. 



" Few, but very great. So that besides the difference of their Number and 

 Position, and of the Liquors which they contain, and Bleed ; there is yet a 

 fourth, and that is, their size. Most of these Turpentine Vessels being of so 

 wide a bore, as to be apparent to the naked eye, and through a good glass above 

 of an inch in diameter. Whereas that of the Lymphseducts can hardly be 

 discovered by the best microscope. 



" The same Turpentine Vessels of Pine are likewise remarkably bigger, not 

 only than the Lymphseducts, but many times than the Milk- Vessels themselves : 

 as those of the Fig, which, in comparison, are exceeding small ; every Arch, 

 not being a single Vessel, but a Parcel or Cluster of Vessels ; whereas one single 

 Gum- Vessel in Pine is sometimes as big as two whole Arched Clusters, that is, 

 as some scores of the Milk- Vessels in a Fig- Tree. And the said Gum- Vessels of 

 Pine, being compared with the Lymphseducts of the same tree, one Gum- Vessel 

 by a moderate estimate, may be reckoned three or four hundred times wider 

 than a Lymphseduct. The like prodigious difference may be observed in the 

 size of the several kinds of vessels of many other plants." 



