1894.] MICROSCOPICAL JOURNAL. 329 



formed of modified epidermal cells is very great. In 

 the geranium leaf there are three distinct types. One 

 of these (fig. 7) is the sharp-pointed, elongate hair. This 

 presents a number of minor but interesting details. 

 First, it is composed of several cells whose transverse 

 walls still remain. These, on their outer side, are thick- 

 ened and so matched as to form a single, continuous, 

 strong wall. If these hairs had no thicker walls than 

 the green cells they would break too easily to be of any 

 use in such exposed situations as this outer surface. 

 Not only are they. protected thus, but they are propped 

 up at their base by a sort of mound of ordinary epider- 

 mal cells (see fig. 7) and are so inserted among them that 

 they are not in danger of being pushed down into the 

 layers beneath. 



The second type of hair is the glandular hair of which 

 a specimen is shown in figure 8. Here a couple of 

 smaller cells hold aloft a larger spherical cell, in whose 

 center iodine demonstrates an evident nucleus and 

 strands of protoplasm reaching out to a lining of the 

 same material. A third type of hair is an elongate hair 

 bearing a globular cell perhaps gladular on the summit. 



But the most remarkable structure in the epidermis is 

 the stoma or breathing pore, of which great numbers 

 occur on each side. Figures 4 and 5 are surface views 

 made by scraping away the green cells and mounting in 

 water a scrap of the epidermis only. Here the ordinary 

 epidermal cells are seen forming a complete mosaic with 

 no breaks excepting where minute oval bodies of cer- 

 tain constant form appear. These consist of two hemi- 

 ovals with a very small opening between them. Sections 

 vertical to the surface may pass through the stomata as 

 shown in figure 2. Figure 10 is a view of a section 

 through a stoma of another plant (Hyacinthus) copied 

 from Sach's Text-Book of Botany. It will be seen from 

 these views that the stomata are really openings which 



