J. A. ARCHER ON TOBACCO. 93 



gathered in a horseshoe shape in the centre of the veins The 

 hairs, also, are short, one-celled, and finely striated, the striation 

 resembling dots. {Fig. 2, pi. 5.) Rhubarb contains a large quantity 

 of raphides, tobacco containing none. 



Rhubarb leaves have always been a favourite adulterant ; they 

 readily take up tobacco liquor, and, when so prepared, have to 

 the naked eye a striking resemblance to tobacco. Less than one 

 per cent., however, is easily detected by the microscope, owing to the 

 abundance of raphides, and the peculiar kind of hair. 



2. Dock. — In dock the bundles of woody fibre are found very simi- 

 lar to those in rhubarb, but more regular. The hairs are one-celled and 

 coarsely striated ; they are also frequently narrower at the base 

 than at the top. {Fig. 3, pi. 5.) Dock contains raphides, like rhubarb, 

 and is readily distinguished from tobacco. Several striking differ- 

 ences may be observed between dock and rhubarb, such as the 

 regular shape of the transverse section of rhubarb and the irregular 

 shape of dock ; the prominences on the dock (in which the cellular 

 tissue is extremely fine), which prominences are absent in rhubarb ; 

 the form, size, and striation of the hairs ; the presence of hairs on 

 all parts of the rhubarb leaf and the absence of them on all parts 

 of dock leaf, except midrib and veins . 



3. Thorn Apple. — The vascular tissue in this plant is arranged 

 in horseshoe form, not unlike tobacco. The hairs, however, differ 

 entirely from tobacco, being of two kinds, sessile and jointed (or 

 glandular and lymphatic). The glandular hairs are very short, 

 consisting of a single cell terminating in a bulb, the bulb resem- 

 bling that on tobacco hairs ; the lymphatic hairs are composed of 

 from two to five joints, terminating in an obtuse point, each joint 

 having the appearance of being dotted over. {Fig. i, pi. 5.) Thorn 

 apple belongs to the same natural order as tobacco. It contains no 

 raphides. 



4. Burdock. — The vascular tissue is arranged in the form of oval 

 bundles. This plant is also distinguished by the form of its hairs, 

 being composed of a large number of short cells, joined end to end 

 in the form of a chain, terminating in a long filament. It is this 

 kind of hair which gives the burdock leaf its soft, downy appearance. 

 {Fig. b, pi. 5.) . 



5. Coltsfoot. — In a transverse section of coltsfoot the vascular 

 bundles are similar in shape to those in burdock, but the number 

 of them is generally limited to three. The hairs are very similar 

 to those of burdock, but shorter in the joints, {Fig. 6, pi. 5.) 



