OF Bacciiakis (.KNISTELI.OIOES fj!)] 



Al'OGEOTKOIMSM 



The stems of /hui/iaris gcnisfi/loidts are markedly apogeo- 

 tropic. A number of the branches of phints 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 /). luiliinifolia, 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 si.x 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 (/. /) 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 pali.sade or spongy 

 tissue. Several rows of chlorophyl-bearing cells packed more or 

 less clo.sely extend inward from both surfaces. The air spaces, 

 which are comparatively few, are chiefly .situated in the middle of 

 the wing. The stomata are appro.ximately 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 ma.ss 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 



