EPIDERMIS. 



41 



a. The Initial cell, bounded by a curved, or even U-shaped wall, is again divided by 

 a wall almost similar to the latter into a Mother-cell and a horseshoe-shaped subsidiary 

 cell (Asplenium bulbiferum', Pteris flabellata (Tig. 14), cretica^); or successively by 2-3 

 curved walls, which alternate in two directions in the surface, and cut one another, into 

 a mother-cell, surrounded by a zone (or in parts a double zone) of half ring- or horse- 

 shoe-shaped subsidiary cells. The longitudinal axis of the subsequent slit is parallel to 

 the chords of the previous curves of division : Cibotium Scheidei (Hildebrand, /. c. Fig. 

 37-39), Mercurialis perennis, ambigua, Pharbitis hispida, Basella, Pereskia aculenta; or 



A 



FIG. 14. — J^eaf of Fteiis Habellata, surface view. A very young, e epidermal cells ; v subsidiary cell, s (close to -v) 

 mother-cell, the other ^ initial cell of the stoma. B almost mature, s guard-cells, v and e z& \n A. From Sashs' 

 Textbook. 



it cuts them at right angles : Thymus serpyllum, Physostegia virginiana, and other Labiatae 

 (Strasburger, /. c). In the last category but one are also the Equiseta. 



b. The Initial cell is divided successively by walls arranged in three directions in the 

 surface into a simple or multiple zone of subsidiary cells, and a mother-cell surrounded 



A 



Fig. 15.— Surface of leaf of Sedum purpurasceus. A young, the initial and subsidiary cells arising by division of 

 the epidermal cells (e) ; in three df the latter the initial cell is just marked off, in four others these are farther 

 divided ; the numbers indicate the successive division walls. B almost mature, e and numbers as in^. From Sachs' 

 Textbook. 



by it. With few subsidiary cells: Papilionacese, Solanaceae, Asperifoliae, Cruciferae; 

 with a large number of them : Crassulaceae (Fig. 15), Begoniaceae ', also Cactacese. 



' Strasburger, I.e. figs. 36-41. 



" Hildebrand, Botan. Zeitg. 1866; Taf. X, fig. 20-23. 



° Strasburger, /. c. — Compare for details this work so often cited ; also the not always precise 

 statements of Karejstschikofif, Zur Entw. der Spaltbffnungen, Bull, Soc, Imp. de Moscou, 1866. 



