ILL US TEA TIONS. 
351 
Plate XV. 
MORPHOLOGY OF FLOWER OF VIOLA TRICOLOR. 
Fig. 93. — Diagram of a flower : (X), the stem ; (K), the leaf ; (B), 
two bracts upon the flower stalk ; then in successive 
circles, sepals, petals, stamens and the united pistils. 
Fig. 94. — Longitudinal section through ovule showing the en- 
trance of the pollen tube through the foramen to the 
embryo sac, the latter wiih a large number of nuclei ; 
around the embryo sac is the nucellus, and around 
the latter are the two coats of the ovule, to the right 
being the raphe. (After Kny). 
Fig. 95. — Epidermal cells from the outer surface of the spurred 
petal showing papilhe. 
Fig. 96. — Epidermal cells from the under surface of the petals, 
some of the cells showing centripetal thickenings, 
the two without thickenings possessing sub-epidermal 
mucilage cells. 
Fig. 97. — Epidermal cells from the under surface of the petals 
showing a zigzag outline and short centripetal thick- 
enings. 
Fig. 98. — ’Surface view of the mesophyl of the petals. 
Fig. 99. — Corkscrew - like hair from the inner surface of the 
spurred corolla near the throat. 
Fig. 100. — A hair from the edge of an anther. 
Fig. 101. — Epidermal cells of the anthers. 
Fig. 102. — Surface view of the mesophyl cells from the spurred 
stamen showing collenchymatous thickening. 
Fig. 103. — Surface view of cells of endothecium. 
Fig. 104. — Natural pollen grain viewed from the side. 
Fig. 105. — Pollen grain examined in water. 
Fig. 106. — Pollen grain observed in chloral solution. 
