CHAP. I. CELLULAR TISSUE. 15 



resemblance to the teeth of a currycomb, in the anthers of 

 Campanula; first noticed by Purkinje. (Plate I. fig. 18.) 



13. Fibres forming distinct arches, as seen in the anthers of 

 Linaria cymbalaria, &c. by Purkinje. (Plate I. fig. 4.)* 



Vasiform Cellular Tissue {Tubes poreiix, Vaisseaux en 

 chapelet, Mirbel ; Tubes corjmsculiferes of Dutrochet.) Tissue 

 of this kind consists of tubes whose sides are marked with nu- 

 merous dots, arranged in a more or less spiral manner, and 

 which are divided internally by transverse partitions. Usually, 

 in addition to the dots, there is distinctly visible an oblique or 

 annular transparent line upon the walls of the tube. (Plate II. 

 fig. 15.17.) Hence Kieser viewed them as spiral vessels, the spires 

 of which, when old, elongate, and become connected by a dotted 

 membrane. BischofF, on the contrary, considers the dots to 

 be caused by the separation of a spiral fibre into extremely 

 minute portions; and he gives a figure (Plate II. fig. 16.) of 

 the manner in which he considers this change to occur. 



It is certain, however, that this kind of tissue, which has 

 been called the dotted duct, is really a modification of cellular 

 rather than of vascular tissue, as was long sin^e asserted by 

 Du Petit Thouars {Ann. des Sciences, vol. xxi. p. 224.); for 

 the following reasons : — If it were such a modification of the 

 spiral vessel as Kieser supposes, it would have none of those 

 internal partitions by which it is particularly known. The 

 same remark applies to the theory of BischofF, which is also 

 imperfect, in not accounting for the nature of the transverse 

 transparent lines that mark the sides of the so-called dotted 

 ducts. Besides, this tissue always terminates abruptly, not in 

 acute cones, as has been seen by myself, and as was first well 

 represented by Griffith, in his excellent illustrations of the 

 anatomy of Phytocrene (Plate II. fig. 19, 20.), and it 

 readily separates at the partitions ; none of which properties 



* According to the last mentioned author, the fibres themselves are 

 generally tubular, and either perfectly round or somewhat compressed, or 

 even three or four sided. He considers it proved that they are hollow, by 

 their appearance when compressed, by their occasionally containing bub- 

 bles of air, and by the difference between their state when dried and when 

 recent. 



