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AMERICAN JOURNAL OF BOTANY 
[Vol. 8 
paratively large carrying leaf which somewhat overhangs the flower. 
The outside of the bract, as well as the stigma and the axil, are covered with 
upward-bent trichomes. These trichomes are of two forms, one a single 
long bristle hair and the other a short, apparently glandular hair with a 
single-celled base and many-celled ovoid head. These hairs are similar to 
those previously described as found on the leaves and stems. Further 
developed flowers, which, with their panicles, are 2 mm. long, have a hairy 
carrying leaf longer than the panicle. The calyx leaves, the petals, and 
the stamens lie alongside each other like small enlargements and finally 
the carpels arise as wall-like growths. In this instance, in which one can 
clearly recognize the construction of the bud, the stamens are egg-shaped 
and are covered by the short petals and the longer calyx leaves. Finally 
the disk shows itself between the gynoecium and the androecium. The 
course of the vascular bundles may very clearly be recognized in the mounted 
material, as resin ducts contained in the phloem have their contents turned 
brown. In the calyx leaf, which is formed with a broad base, 5 ribs appear 
of which the middle one is the strongest and most branched. On the 
other hand, the petal, which has a small base, has only one short, weak or 
unbranched rib on each side of the strongly branched midrib. 
The disk appears in longitudinal section as a wide, somewhat sunken 
cushion. Toward the bottom its tissue is large-celled; above, on the other 
hand, it consists of small, closely united, plasma-rich cells, of the sort com- 
mon to glandular tissues. Many small crystal clusters lie on the border 
of both tissues and in the upper, small-celled tissue, but are lacking in the 
lower, large-celled tissue. The epidermis consists of rather small polygonal 
cells and contains numerous stoma-like apertures whose guard cells are 
almost always larger than the other epidermal cells. A small space is 
found under the stoma-like opening. These openings apparently do not 
serve for gaseous interchange, but for the excretion of a glistening and 
strongly aromatic fragrant nectar whose existence has already been men- 
tioned. 
The development of the stamens in pistillate and staminate flowers is 
apparently similar to the time of the formation of pollen mother cells. 
In the pistillate flower no pollen grains are formed, the anthers remain 
empty, and have a shrunken appearance. The filaments of the pistillate 
flower remain as short as those of the staminate flower until the flowers open. 
The stamens naturally develop further in the latter. Pollen formation 
occurs in the anthers but shows nothing particularly noteworthy. The 
vascular bundles of the anthers contain no resin ducts, these having ended 
half-way up the filaments. The anther is also to a certain degree the only 
organ of the plant which has no resin-like or poisonous sap. It is not sur- 
prising then that the pollen has no toxic action on the human skin (17). 
Similar observations have been made by Inui (10) on the pollen of Rhus 
vernicifera, by Warren (29) on that of R. Vernix, and by Rost and Gilg (24) 
