252 The Ohio Journal of Science [Vol. XVI, No. 7, 



area, lying nearer to the stem side of the petiole than the outer 

 side. A segment from the middle of this region is shown in 

 detail (PI. XVI, Fig. D), extending from the epidermis on the 

 side away from the stem axis, to a point on the inner side of 

 one of the bundles. 



The cortical cells and the epidermal cells show definitely 

 thickened walls; a non-lignified type of thickening, however. 

 These walls possess simple pits (not numerous). Scattered 

 bast fibres are found in the inner cortical region, whose walls are 

 not as thick, however, as those of the stem. 



The phloem and xylem show no special characteristics. 

 Tracheae and tracheids make up the body of the xylem, the 

 tracheids being larger than many of those found in the stem 

 and those found in the leaf. 



The Stem. Figs A and B, PI. XII, show the transverse and 

 longitudinal, radial sections, respectively, of the one year old 

 stem in winter condition. The cork layer is of the common 

 type. The phelloderm is one cell layer thick. True collen- 

 chyma is but weakly developed, consisting when found in a 

 favorable section, of but a single layer of cells of the outer 

 cortex, with thicker walls than those beneath it. Since the 

 cortex cells inward as far as the scleride and crystal "sac" 

 layer, have definitely thickened walls, the differentiation 

 between them and the collenchyma is ill defined. These 

 cellulose-thickened walls show minute inter-cellular spaces 

 between, but the simple pits which doubtless are present in 

 them could not be definitely demonstrated as were those of the 

 petiole cortex. 



On its inner side the zone of cells just described (primary 

 cortex) is sharply delimited by a layer two or three cells thick 

 (typically) containing two kinds of elements ; sub-isodiametrical 

 sclerides or stone cells and cuboidal to slightly tangentionally 

 flattened cells, each containing a monoclinic crystal of calcium 

 oxalate. See Figures labeled with abbreviations. This scleride- 

 containing cylinder of tissue is of especial interest because 

 similar types of sclerenchymatous elements occur massed in 

 various forms in most of the galls to be described hereafter. 

 The region of the nodes, (particularly best developed in the 

 cortex of the "angle") shows these two kinds of elements 

 developed in sub-spherical masses. 



