28 



STRUCTURE AND LIFE-HISTORY OF HAY-SCENTED FERN. 



la the following table the depth is measured from the ridge of entrance down to 

 the deepest dorsal focus. The stoma was closed by displacing water with alcohol. 



[P- 35] The first effect of the alcohol is to widen the pore, which then gradually 

 closes, the sides becoming apparently straight before they meet. The increase in depth 

 at the ends, which is partly responsible for opening the pore of this stoma, works to 

 better advantage than in the stoma of Osmunda. 



The cells of the lower epidermis (.fig. 111) are smaller and more wavy 

 than those of the tipper surface. All of the epidermal cells contain chloro- 

 plasts, but they are especially abundant in the guard-cells. The thickness 

 of the lamina runs from 0.06 mm. at the veinlets to 0.09 mm. where the 

 mesophyll is well developed. The air-spaces are especially large in the 

 lower half of the spongy parenchyma. A continuous layer of irregular 

 cells lines the upper epidermis, but there is nothing that could be called 

 palisade tissue (fig. 113). 



Scattered plentifully all over the leaf are hairs of two kinds acicular 

 (fig. 258, b} and glandular (figs. 105, 113, 249). The first are simple, acute, 

 septate, often 1 to 2 mm. long. The latter are simple, septate, with a 

 spherical terminal cell, and from 0.08 mm. to 1 mm. long. The terminal cell 

 (or sometimes two cells) is surrounded by a globule of secretion. In this 

 doubtless resides the ethereal oil which gives the characteristic scent to 

 the plant. Waters (1903, p. 290) states that the odor is stronger in plants 

 grown in dry, sunny places than in those grown in shade, and that it is 

 changed and intensified in drying the leaves. By "distilling with steam" 

 a "considerable quantity of the partly dried ferns, . . . two or three 

 drops of oil were obtained ... It had a rather disagreeable odor, but 

 when a drop or two of a solution of the oil in a large amount of ether was 

 put on paper and the ether allowed to evaporate, a very pleasant reminder 

 of 'new-mown hay' resulted" (Waters, 1903). One bottle of fronds pre- 

 served in 50 per cent alcohol has retained the odor strongly, and it adheres 

 very persistently to hands or clothing after the alcohol has evaporated. 



The leaf -shoot, several times referred to above, attracted my attention 

 in the fall of 1901 . It is the stem which comes off from the base of the petiole 

 (fig. 4). About 20 per cent of the leaves bear siich shoots, the remaining 

 80 per cent showing no trace of them whatever. The shoot arises on the 

 side of the petiole at a very early stage of development, but I was not able 

 to find its relation to the sectioning of the segments of the leaf. I believe 



