i! STUDIES IN HISTOLOGY. 



broad statement ; for instance, preparations of nascent flowers 

 are shown equallj- well bj- shaded figures, and the same is true 

 of maiij- pollen-grains, etc. The use of slips of drawing-paper 

 of uniform size and the arrangement of these under appropriate 

 heads will render the keeping of a systematic record of work 

 much easier. 



Permanent preparations. In most cases the sections or other 

 preparations should be permanently mounted in some suitable 

 preservative medium, and properly labelled with the name of the 

 plant and of the special part exhibited, date of preparation, 

 medium in which it is mounted, etc. The drawings should be 

 numbered or labelled to correspond with the permanent prepa- 

 rations. 



Histological elements, their modifications and combinations. 



In the following enumeration of the more important elements 

 the sequence is (1) form, (2) contents, (3) distribution, (4) 

 development. 



FOEMS OF THE STRUCTURAL ELEMENTS AND SIMPLE 



TISSUES. 



1. Pakenchyma Proper and its Chief Modifications. 



(a) Soak a few peas or beans in water until they become soft 

 enough to be cut without difficulty, remove the seed-coats, and 

 make with a wet razor (see 8) three very thin sections through 

 the cotyledons. These sections for comparison should be at right 

 angles to one another, in order to exhibit the length, breadth, 

 and thickness of the cells. On removing them from the knife 

 or razor (by means of a camel's-hair brash), float them in water 

 and move them genth' about, in order to detach the cell-contents 

 which have partly escaped fiom the cut cells. When the sections 

 appear clear, transfer them to the middle of a glass slide, add 

 a little pure water and cover with thin glass, being very careful 

 to exclude all air-bubbles. If the sections are thin and wholly 

 free from bubbles of air, compare the outlines of the cells with 

 one another, making drawings of the specimens. 



(b) Make similar sections (1) through the pulp of an}^ unripe 

 fruit — apple, pear, snow-berry, etc. ; (2) through the pith of 

 Elder, Lilac, or any soft shoots ; (3) through the pulp of any 

 succulent leaves, for instance those of Sedum, Purslane, or 

 Beoonia. 



