106 THE UNIVERSITY SCIENCE BULLETIN. 



about .5 mm. apart. The tracheids are of three kinds, spiral, an- 

 nular, and reticulate (figs. 84, p", q", and r"; and 85, p", q", and 

 r"). 



The xylem, phloem and border parenchyma cells of a vascular 

 bundle of the leaf are shown in cross section in fig. 72. The border 

 parenchyma cells in leaves, which were left in 5 per cent potas- 

 sium hydroxide solution for bleaching, are shown in tangential 

 section in fig. 79. The pits in the end walls of these elongated 

 cells are not conspicuous in unbleached sections (fig. 86). 



The vascular system of the petiole is made up of separate vas- 

 cular strands. This is shown in the cross section of a petiole from 

 the base upward in figs. 87 to 89, inclusive, in which the five 

 vascular strands are mapped out. The cross section of the petiole 

 in fig. 87 was cut from the base of the petiole; fig. 88, midway 

 between the base and tip of the petiole; and fig. 89, from the tip 

 of the petiole. Each vascular strand has a sheath of border 

 parenchyma. A cross section of two of the vascular bundles of 

 the petiole is shown in fig. 90, j. Petit {fide Solereder, '08) has 

 found that isolated vascular bundles form the vascular system of 

 the petioles in species which he examined in the genera Artiplex, 

 Blitium, and Chenopodium. 



In the figs. 91 to 95, inclusive, there is mapped out a series of 

 portions of the cross sections of the stem from below the petiole 

 attachment to a little above. The five leaf-trace bundles are 

 mapped out in fig. 91. In fig. 92 the leaf traces are crossing out 

 of the stem into the petiole. Successive steps in the closing of the 

 leaf gap are shown in figs. 93, 94 and 95. 



NATURE OF THE CELL CONTENTS. 



The Stem. 



Distributed through the protoplasts of the cells of the epidermis, 

 and of the collenchyma and parenchyma of the primary cortex, 

 there are quite a number of large globules (and many small 

 globules) which stain like oil with Sudan III and alcannin (fig. 

 9, q'). Similar globules are present in the cells of the phloem of 

 primary vascular bundles, and of the phloem and secondary 

 medullary rays of the anomalous tissue. The globules in newly 

 cut sections of formalin material, left in Sudan III for twenty- 

 four hours, stained red; in alcannin, pink. Some of the globules 

 in sections which had remained in xylene, chloroform or ether for 

 twenty-four hours, and were then left in either of the two stains 

 mentioned above, stained as before, but nearly all the globules 



