24 STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 
opment occurs in May and June. Two to five leaves is the common annual 
growth from each branch of the stem. With considerable accuracy each 
leaf faces the chief source of light. When growing around an old stump 
or a bowlder, the leaves on every side turn their backs to it. On steep 
hillsides, also, the leaves face downhill. While not every leaf, by any 
means, stands thus, the general effect is very noticeable. The leaves stand 
nearly erect, but the blade is gently curved backward. A leaf which ma- 
tures in June (first crop) turns yellow in August or September in eastern 
Pennsylvania and Maryland, by reason of old age (whatever that may be). 
In New England the first leaves persist throughout the season. The first 
sharp frost kills all of the foliage of Dennstedtia. 
TABLE 6.—Data of the leaf. 
Length of— Maxi- |Distance of No. of Maxi- 
No Total mum __ |widest part} Diameter ‘airs of | um No. 
: length. |————-———_| width of | from base |of petiole. Lane of pairs of 
Petiole.| Blade. lexf. | of lamina. P * | pinnules. 
cm. cm. em, em. em, mm, 
1| 4.11 23 88 21 24 26 46 24 
2 53 13 40 16.3 15 Ds2 37 22 
3 33-5 7 26.5 6.8 12 1.8 30 13 
4 41 To 31 1.7 12.5 1.8 32 19 
Av.of 10 60.38 | 14.2 | 46.18 16.49 15-7 2.02 37-5 21.5 
The petiole is slender, smooth, “‘chestnut-brown’’ (Clute, 1901), chan- 
neled on the upper (ventral) surface, about one-fourth of the total length 
of the leaf (not one-half, Clute, 1901). It is slightly stouter at base, e. ¢., 
3 mm. in diameter below and 2.5 mm. above. The lower part is nearly 
always curved, often very much so, because of the obstructions the leaf 
meets in coming out of the soil. Above the earth it is straight and nearly 
erect. 
The brown color of the petiole is due to pigment (phlobaphene ?) in the 
cell-walls of the epidermis and outer cortex. At the base, the cortex may 
be colored to a depth of nine cells. Passing upward along a newly ma- 
tured leaf, the layer grows thinner, and just below the first pinnze there is 
often no pigment at all. But the coloring advances upward with the age 
of the frond, until all of the rachis may become brown. The epidermal 
cells are very irregular in size. Near the rhizome they are polygonal and 
are about twice as long as broad. They become longer above. At 1 cm. 
from the rhizome they are five times, and just below the blade seven to 
eleven times, longer than wide. In transverse section (fig. 69) they are 
nearly isodiametric, but of very different depths. Each cell bulges out a 
little on the surface of the petiole. The cell-walls are thickly lignified, 
and bear numerous pits suggesting a continuity of protoplasm from cell to 
cell. There are many hairs, both glandular (fig. 249) and acicular (fig. 
258, 6) on the young petiole, but they wither or are completely shed at 
