308 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
Explanation of Plates. 
All figures were made by aid of the camera lucida. The arrow tip points in 
the direction of the apex of the root. The letter e attached to drawings of 
radial longitudinal sections indicates the external border of the section. 
PLATE 16. 
Fig. 1. Aneimia adiantifolia. Radial longisection of epidermal cells under 
the cap. The first trichoblast at T. X 410. 
Fig. 2. A. adiantifolia. Rudiments of the trichomes immediately back of 
the cap. X 220. 
Fig. 3. A. adiantifolia. Surface view of young trichomes. X 160. 
Fig. 4. Longisection of the growing tip of a root of Azolla filiculoides (micro¬ 
tome section from material embedded in paraffin) ; T, trichoblast. 
X 450. 
Fig. 5. A. filiculoides. Origin of the hair initials ; close of mitosis and 
forming cell plate are seen at d. X 750. 
Fig. 6. A. filiculoides. Trichoblasts and intervening cells at the beginning 
of the growth of the hairs, about ten cell pairs removed from the 
oldest shown in figure 4. X 450. 
Fig. 7. A. filiculoides. First transverse division of intervening cell. X 450. 
Fig. 8. A. filiculoides. Young root-hairs seen in tangential section of the 
root, showing zonal arrangement. X 450. 
Fig. 9. A. filiculoides. Young hairs in radial longisection, separated in the 
row by four intervening cells. X 300. t 
Fig. 10. A. filiculoides. Base of mature hair, between elongated epidermal 
cells. X 450. 
Fig. 11. Extremity of the root of Azolla filiculoides. X 5. 1 
Fig. 12. Equisetum arvense. Radial longisection of young epidermal cells, 
showing the origin of the trichoblast at T. The root-cap over- 
lies these cells. X 410. 
Fig. 13. E. arvense. Radial longisection of the epidermis a short distance 
from the root-cap. X 265. 
Fig. 14. E. arvense. Tangential section of the epidermis before the emer¬ 
gence of the hairs. X 265. 
Fig. 15. E. arvense. Young trichomes in longisection. X 265. 
Fig. 16. Lycopodium inundatum. Radial longisection of cells lately divided 
for the formation of trichoblasts (T), lying under the root-cap. 
X 300. 
Fig. 17. L. inundatum. Growth of the root-hairs. X 265. 
1 Figure 4-11 are here used by courtesy of the Botanical gazette. 
