66 



Elementary Plant Physiology. 



up/ 



Fig. 42. — Transverse section of leaf of 

 Russian thistle (Salsola Tragus). /, pali- 

 sade parenchyma ; «/, single layer of small 

 parenchyma cells ; w, water storage tissue ; 

 r, reduced fibrovascular bundle ; (?, epider- 

 mis : v^ vessels of larger fibrovascular bun- 

 dle ; hy trichome. After Pammel. 



Sedum, Portiilaca, 

 Othoniia, or any 

 convenient form. 

 Note the features to 

 which attention has 

 been paid in the 

 above examinations, 

 and also look for 

 cells which might 

 serve for the storage 

 of water. 



60. Structure 

 of a cladode — 

 Examine the leaf- 

 like expansions 

 borne by the " smi- 

 lax " of the florist, 

 or the needle-like 

 branches serving for 



[Salsola Tragus), Tissa 

 ricbra, ^.n^ Ambrosia (rag- 

 weed) will be convenient 

 examples. Are loosely ar- 

 ranged parenchyma cells to 

 be seen, and are the stoma- 

 tal openings of the same 

 character? Estimate the 

 number of stomata per 

 square centimeter. 



59. Structure of a 

 succulent leaf. — Exam- 

 ine, as above, the leaf of 

 some succulent such as 



Fig. 43. — Branch of Asparag-us medeloides (smilax) 

 with flattened cladodes. After Reinke. 



