PLATE XXXVI. 



Fig. 1. Tangential section of Populus alba with pits in wall between 

 medullary ray and phloem parenchyma and between two pa- 

 renchyma cells. 



Fig. 2, Side view of obliquely placed end sieve plate from Populus alba 

 and with pits between the sieve tubes and the other phloem 

 cells. Tangential section. 



Fig. 3. A pit in a vertical wall between a medullary ray and the phloem 

 of Populus alba. 



Fig. 4. Transverse or reticulate strengthening bands on the wall of a 

 sieve tube in a root of Populus deltoides. Tangential section. 



Fig. 5. Transverse bands on the wall of a sieve tube in the root of 

 Populus deltoides, as seen in section. 



Fig. 6. Transverse section in Amorpha fruticosa, showing the radially 

 elongated medullary-ray cells and others similar to these 

 sweeping around the narrow strip of phloem and arranged 

 to conduct food from these radially, especially to the cambium. 



DESCRIPTION OF FIGURES. 



Plates XXXVI and XXXVII. 



Explanatory notes: Magnification is 600, except in figure 6, where it' is 



250 approximately. 

 Lettering: st = sieve tube; m = medullary ray; p = parenchyma; 



camb = cambium; stch = starch; cr = crystal; pt = pit; n = 



nucleus. 

 Symbols: -^ ) and — > J = direction toward nearest point of circun^- 



f^reijce or in the epidermis, 



