LEAVITT: TRICHOMES OF ROOT. 
309 
Fig. 18. L. inundatum. Bases of the trichomes in radial longisection. x 
220 . 
Fig. 19. L. inundatum. Tangential section of epidermis, showing bases of 
the trichomes. X 220. 
Tig. 20. Lycopodium lucidulum. Radial longisection of the epidermis show¬ 
ing the origin and development of the trichoblasts. T, the first 
trichoblast. X 410. 
Fig. 21. L. lucidulum. Earliest stages of trichoblasts, seen tangentially, x 
410. 
Fig. 22. L. lucidulum. Longitudinal division of the trichoblast. 
PLATE 17. 
Fig. 23. 
Fig. 24. 
Fig. 25. 
Fig. 26. 
Fig. 27. 
Fig. 28. 
Fig. 29. 
Fig. 30. 
Fig. 31. 
Fig. 32. 
Fig. 33. 
Fig. 34. 
Fig. 35. 
Fig. 36. 
Fig. 37. 
Fig. 38. 
Fig. 39. 
Fig. 40. 
Isoetes canadensis. Superficial view of the young epidermis, in the 
region of the formation of trichoblasts, beginning with the 25th 
cell (c) from the apex of the root. The trichoblasts (T, T, etc.) 
are distinguished by relatively dense contents. X 410. 
I. canadensis. The trichoblast and three atrichomic cells of the 
same group, in longisection. X 410. 
I. Engelmanni. Trichomic and atrichomic cells in longisection in 
the region in which the hairs begin to appear. X 240. 
Isoetes sp. Young elongating epidermis at the edge of the root-cap, 
in superficial view. X 260. 
I. foveolata. Superficial aspect of the mature epidermis. X 220. 
Selaginella rupestris. Optical longisection of the epidermis at the 
edge of the cap. T, the first trichoblastic segment. X 410. 
S. rupestris. Bases of trichomes. X 260. 
S. denticulata. Part of an epidermal cell row in surface view. X 
260. 
Limnocharis emarginata. Longisection of the epidermis beginning 
with the 18th cell from the apex. The first trichoblastic division 
at T; b continues a with a slight break. X 260. 
L. emarginata. Trichoblasts in tangential section, before the appear¬ 
ance of root-hairs. X 260. 
L. emarginata. Lower part of mature trichome. X 260. 
Triglochin maritima. Base of trichome. X 490. 
Ruppia maritima. Base of trichome. X 490. 
Zannichellia palustris. Base of trichome. x 490. 
Naias gracillima. Tangential section of epidermis, showing lately 
formed trichoblasts (as at T). X 410. 
N. gracillima. Longisection of epidermis near the edge of the cap. 
X 315. 
N. gracillima. Development of the root-hairs. X 315. 
N. gracillima. Superficial view of the epidermal cells immediately 
back of the root-cap. T, the young trichome. X 220. 
