x 
268 BOTANICAL GAZETTE. [ October, 
heavy-walled ones spoken of above. After acting as an 
almost complete partition in the region mentioned, it gre 
to merge into the phloem on either side. The cells pai: 
up this curious structure are rather thin-walled, and abou 
Just what the office of these cells can be, I am not rae 
to say. They may be active meristem cells, an i 
growth of the internode may be found in this layer. i 
found that wherever this exists it forms a line of easy | 
vision, and the brittle stems always break at this. ge 
If the other habits of the plant would warrant it, this ae 
be a means for propagation, since by breaking as al pas 
there can be no injury to the node, and if the plant “ae 
from cuttings this may be nature’s way of providing them. 
Crawfordsville, Ind. 
EXPLANATION OF PLATE XXI AND FIGURES IN TEXT.—Fig. 1. are 
section of stem: e, epidermis; c,cortex; }, bundle sheath; ph, phloem; ai ; 
xylem; p, pith; sc, sclerenchymatous fibers; s, 8, 8, stomata; 4 % a, 
chambers. pn 
Fig. 2. Surface section of epidermis, showing vertical rows 0 
Fig. 3. Epidermal cells surrounding a stoma. : 
Fig.4. Cross section of stoma: s, stoma, guard cells below; 
chamber ; e, epidermis; sc, sclerenchymatous fibers. 
Fig. 5. Guard cells dry. 
Fig. 6. Same, partly closed. 
Fig. 7. Same, nearly swelled shut. 
Fig. 8. Longitudinal section of stoma. ; 
Fig. 9. Longitudinal section of stem, lettered as in fig. 1. 
Fig. 10. Elements in longitudinal view: sc, sclerenchym 
sp, long tracheid; tr, forms of tracheids; 7, pith. ae jon. 
ig. 11. Showing diaphragm above node as in longitudinal sect 
Fig. 12. More highly magnified portion of same. 
Figures 3—8, < 250; 1, 2, 9, 10, 12, X 125; 11, x 24. 
a, ait 
atous fiber; 
salen Sgn teat Oe 
