OF BACCHARIS GENISTELLOIDES 691 
APOGEOTROPISM 
The stems of Baccharis genistelloides are markedly apogeo- 
tropic. A number of the branches of plants which have been 
grown in a moist greenhouse have fallen down from their own 
weight. In all cases, however, the tips have turned perpendicularly 
upwards, and the plants present a very striking appearance in con- 
sequence. They are markedly different from the diageotropic 
shoots of B. halimifolia, which is growing in the same place. That 
this falling down of the branch is also characteristic of the plant 
in its natural environment is seen from herbarium specimens. 
There are often as many as six upright branches from one pros- 
trate one. 
THe WING 
The wings are the conspicuous portion of the plant ; they vary 
in width from a few millimeters at the youngest portions to 2 cm. at 
the older. The length depends upon their relation to the internodes. 
As shown above (f. 7) some wings go through only one, others 
through two internodes, the longer ones being from 10-18 cm., 
the shorter from 3-8 cm. A transverse section (/. g) shows a 
very compact structure. There is no definite palisade or spongy 
tissue. Several rows of chlorophyl-bearing cells packed more or 
less closely extend inward from both surfaces. The air spaces, 
which are comparatively few, are chiefly situated in the middle of 
the wing. The stomata are approximately equal in number on 
both sides of the wing, averaging 70-80 to the square millimeter. 
The wings are notably rigid; this is due to the occurrence of 
strands of mechanical tissue which are developed in connection 
With the vascular bundles. The conducting tissue plays but an 
unimportant role in the support of the wing. There is a particu- 
larly large stereome mass on the extreme edge, which is readily 
removable as a thick thread. 
In order to determine the morphology of the wing, serial sec- 
tions of the growing point were prepared. From these it appeared 
that the wings are directly continuous with the margins of the 
scales. On comparison with shoots bearing true leaves this view 
was substantiated. In the terms of many of the text-books, then, 
these wings would stand as ‘“decurrent leaves’ —as elaborations 
