SUNFLOWER STEM 59 



leaves opposite, leaf-trace with 1 bundle. Clematis, leaves 

 opposite, leaf-trace with 3 bundles (Fig. 3). Stackys, leaves 

 opposite, leaf-trace with 2 bundles. 



The method which has above been recommended in Helianihus 

 is a coarse one, and only available in stout herbaceous Dicotyle- 

 dons. When such a method is used it should always be checked 

 by comparisons of longitudinal sections of the apical bud. As a 

 rule the subject should be studied in the first instance by making 

 such longitudinal sections. These should be thick, and be cleared 

 by treatment with dilute potash, or " eau de javelle." Where 

 the bud is not too bulky, Naegeli adopted the method of bisecting 

 the bud, clearing with potash, and drawing the bundle-arrange- 

 ment in the two halves ; the whole bundle-arrangement at the 

 apex can be deduced from two such sections. As a further con- 

 trol, series of transverse sections should be cut through the apical 

 bud ; the order of these and their relative position must be 

 accurately marked. A diligent comparison of these (with 

 drawings) will supply the data for deducing the whole bundle- 

 system. Finally, the results obtained by these two methods 

 should coincide, if the observations be correct. 



An examination of the vascular system of a young seedling of 

 the Sunflower will serve as a simple example of the method of 

 study of a bundle-system by means of successive transverse 

 sections. 



Take Sunflower seedlings in which the cotyledons have escaped 

 from the seed, but in which the plumule is not yet far advanced : 

 after treatment with alcohol, soak them for twelve hours in dilute 

 glycerine. 



Prepare a slide, by covering it, where the cover- slip will be 

 placed, with a thin layer of glycerine jelly : now wet a razor 

 with dilute glycerine, and cut successive transverse sections 

 through the base of the cotyledons and the upper part of the 

 hypocotyledonary stem, keeping them carefully in their right 

 order on the razor : transfer them in that order to the slide, warm 

 gently and cover : compare the sections under a low power, and 

 make drawings of them. There may be slight differences in 

 detail, but the main points to be noticed are these : 



1. The leaf-trace of each cotyledon consists of one median 



