STRONG DRINK AND TOBACCO SMOKE. 15 



order to obtain our ground plans and sections. This is 

 accomplislied by making careful sections of tlie plant 

 from every part of it and in every direction of its growth, 

 and submitting tliese to tlie searching power of the 

 compound microscope, in order to view the structure 

 from every point. For instance, a thin slice of the 

 young green stem of barley cut horizontally (at a right 

 angle to the direction of its growth), and placed in 

 water on the stage of the microscope, will show whether 

 the woody {Jihro-vascular) tissues lie together in one 

 mass, or are scattered in small w^edge-shaped bundles 

 (Plate 2, fig. 14). A thin slice from the same stem, 

 cut vertically in the direction of its growth (Plate 2, 

 fig. 15), will show the composition of its tissues, and 

 from this, individual cells and vessels can be carefully 

 dissected out under the dissecting microscope with 

 tw^o fine needles, for examination under the compound 

 microscope, when their beautiful transparency will render 

 their minutest structure very evident. If, in cutting 

 these sections, the knife blade should by accident pass 

 through (as it will do frequently) some part of a minute 

 vessel in a somewhat slanting direction, the student 

 will be rewarded with a view of a part of the in- 

 terior of it, and will thus be enabled to compare 

 the appearances of both surfaces. In fact, in this as 

 in other matters, chance or accident w^ill sometimes 

 accomplish for us that which our most patient labour 

 Avill not. 



