PLATE 39 
1. —Enlarged cross section of a rather regular portion of the second xylem- 
phloem ring in Ricinus communis (PI. 37, fig. 2). The normal xylem-phloem ring 
is in the direction of the arrow. Cambium and phloem at the top. Twisted spiral 
vessels at X. Tracheae properly oriented at Y. X160. 
2. —From the same vascular ring, as figure 1, showing tracheae lying at right angles 
to the longer axis of the stem, as often happens in crowngalls, and others properly 
oriented. Phloem at the top. Same magnification. 
