CHAPTER VIII. 



THE MONOCOTYLEDONOUS STEM, AND CLOSED COLLATERAL 

 VASCULAR BUNDLES. 



PRINCIPAL MATERIALS USED. 



Stems of Zea Mais (Maize, or Indian Corn) ; in alcohol. Or, stems of Oat, 



or other grass. 

 Full-grown leaf of Iris florentina, or the Flag Iris, in alcohol, and laid for 



twenty-four hours in half-and-half alcohol and glycerine. Also fresh 



material. - 

 Stems of Draccena (Cordyline) rubra : fresh ; also in alcohol. 



PRINCIPAL REAGENTS USED. 



Chlorzinc iodine Soda corallin Safranin Various stains for single or 

 double staining Borax- carmine and methyl-green Hydrochloric acid. 



Stem of Zea Mais. A very favourable object for the study 

 of tbe structure of the closed collateral vascular bundles of 

 Monocotyledons is the stem of the Maize or Indian Corn (Zea 

 Mais). We will examine material which has lain for some time 

 in alcohol, in order the more readily to study the cell-contents 

 at the same time. First prepare a cross-section, taking care that 

 it passes through an internode and not through a node. We 

 shall understand the structure more easily if the section is laid 

 at once into a drop of chlorzinc iodine. Coloration of the 

 section begins at once, and the separate vascular bundles stand 

 out quite clearly even to the naked eye. If we lay the glass-slide 

 on a white background (e.g., a sheet of paper), we can in the 

 simplest possible way see the isolated (or scattered) arrange- 

 ment of the vascular bundles ; an arrangement, as a whole, 

 peculiar to Monocotyledons. It will also show that the vascular 

 bundles are more closely crowded together towards the periphery 

 of the stem. Every vascular bundle shows in cross-section as 

 an oval spot ; the tissue in which these bundles are embedded 



(101) 



