THE SPERM APHYTES. 



227 



FIG. 145. Portion of a cross section of a 

 leaf of the Rubber Plant, Ficus elas- 

 tica. A, epidermis of upper side of 

 leaf ; B, palisade parenchyma ; C, 

 spongy parenchyma or mesophyll; D, 

 epidermis of under side of leaf ; under 

 E is a fibrovascular bundle ; F, a cysto- 

 lith ; G, a stoma with cavity above it. 



elastica. In that figure A is the epidermis of the upper 

 side of the leaf. B is two rows of more or less rectangular 

 cells of the palisade parenchyma. C is the spongy paren- 

 chyma which constitutes the greater part of the interior 

 of the leaf. D is the 

 epidermis of the under 

 side of the leaf. E is a 

 section through a fibro- 

 vascular bundle which 

 forms the rib of the leaf. 

 F is a cystolith, an aggre- 

 gation formed by parti- 

 cles of carbonate of lime 

 which have collected on 

 a mass of cellulose that 

 has formed here abnormally ; it is supported by a stalk 



from the surface of the 

 cell in which it has 

 formed. 6r is a sec- 

 tion through a stoma. 

 3. Study Fig. 146, 

 which is a transverse 

 section of the stem 

 of a house Geranium, 

 Pelargonium. It rep- 

 resents the herbaceous 

 type of dicotyledonous 



FIG. 146. Portion of the cross section of the stems. E is a single 

 stem of a House Geranium, Pelargonium. . .. .. , 



A, pith parenchyma ; B, cambium layer ; TOW ot Cells O the epl- 



C, cortical parenchyma; D, cork layer; dermis with proiect- 

 E, epidermis ; F, xylem ; G, phloem. 



ing hairs. At D are 



several layers of cork cells. is the cortical parenchyma. 

 G- is the phloem or inner bark. B is the cambium layer 

 and is composed of extremely delicate, radially flattened 

 cells. F is the xylem or wood, which in this plant forms 



