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 1 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 Dennstcedtia. 



TABLE 6. Data of the leaf. 



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. g., 

 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 pinnae 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 polyg'onal 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, b) on the young petiole, but they wither or are completely shed at 



