1894.] MICROSCOPICAL JOURNAL. 331 



the size which might be attained by the mere increase of 

 cells of this description ; at tthwa tpbnilcuheampts life 

 on laud must be able to protect these worker cells or be 

 destroyed. It is thus very clear that noly plants with 

 support and protection for the delicate worker-cells could 

 exist on land, and such only could propagate. There are 

 some plants which live on land, in a certain sense. They 

 lie prone on rocks and are found in damp or wet places 

 and yet have little besides the mass of worker-cells. 

 Such are insignificant and lowly forms mostly unknown 

 beyond the acquaintance of the botanist ; but trees, and 

 shrubs, and flowering herbs, all owe their power to live 

 the life they do to the presence of epidermal structures 

 and to the supporting fibro-vascular tissue. 

 Hamline Biological Laboratory, September 20, 1894. 



EXPLANATIOX OF THE FRONTISPIECE. 



These figures are drawn from camera lucida tracings. The accompanviug 

 scale of one-thousandths of an inch permits direct measurement of the cells. 



Fig. 1. Cross section of leaf passing through a vein (partly diagrammatic) . 



Fig. 2. Small portion of figure 1 magnified 260 diameters. Ep, epidermis. 

 The upper side is up. Pal, palisade cells on the lower sive 

 the section passes through stoma. A small portion of a fibro- 

 vascular bundle is shown. 



Fig. 3. A portion of the fibro-vascular bundle seen lengthwise showing 

 the junction of two spiral-cells, and the shrunken protoplasm in 

 one of the parenchyma cells. 



Fig. 4. Surface view of the cells of the epidermis of the upper side, show- 

 ing two of the stomata. 



Fig. 5. Similar view of the under side, epidermis and stomata. 



Fig. 6. Epidermis cells in section after treatment with dilute acid to 

 shrink and demonstrate the protoplasm ; cut the greatly thickened 

 external wall of the cell ; pp, the protoplasm. 



Fig. 7. One of the hairs showing the wedged-form base and mound of or- 

 dinary epidermal cells around it. 



Fig. 8. A glandular hair in the outermost cell, a nucleus and vacuolated 

 protoplasm. 



Fig. 9. An elongate glandular hair, intermediate type between the other 

 two. 



Fig. 10 View of the stoma guard-cells showing the protoplasm in situ. 

 Copied from Sa«h's Text-book. 



