ILLUSTRATIVE STUDIES 



119 



ILLUSTRATIVE STUDIES 



i. Study longitudinal radial sections of old Aristolochia 

 stems made into permanent mounts and double-stained in ery- 

 throsin and iodine green or in safranin and haematoxylin ; or 

 if fresh sections are used mount them in aniline sulphate. Note 



O 



oo o 



c 



O 



D 



FIG. 6 1. Camera-lucida drawings of equal areas of cross sections of stems of .4, hop; 

 B, yellow poplar; C, water cress, and D, Psidium Galapageium which grows in a perpetually 

 dense fog. The first two stems have need to carry relatively large quantities of water, and 

 the last two relatively little. Only the tracheal tissues are here outlined. 



the spiral and annular tubes next to the pith that have been 

 formed by the procambium, and the different pitted kinds that 

 have been formed by the cambium farther out. Draw the 

 different kinds and let the drawings of the tangential walls, 

 namely, those that are on edge in the radial section, show clearly 



