692 KupFER : ANATOMY AND PHYSIOLOGY 
of the leaf-base, named by Vines the ‘‘hypopodium.”’ Their pe- 
culiar phyllotactic arrangement would thus obviously be explained. 
The question was raised however as to whether these facts alone, 
7. e., the connection with the leaf-base and their phyllotactic rela- 
tion, would be sufficient to establish the homology with leaf- 
structures. The point was decided in the negative for the follow- 
ng reasons : 
1. Their main axes, even at the growing point, are parallel to 
the stem, instead of at a greater or less angle as in other developed 
leaf-bases, 7. ¢., stipules. 
Oo 
29 Nees 
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Fic. 9. Cross-section of wing Fic. 10. Cross-section of leaf 
of Baccharts genistelloides. of Baccharis genistelloides. 
2. In many plants, Lathyrus latifolia, L. sylvestris and L. 
grandifiorus among others, both stipules and wings occur. In 
such cases the wings, although just as obviously continuous with 
the wings of the petiole, evidently could not be hypopodia. 
3. Other organs have been found that follow the leaf arrange- 
ment, but may not therefore be supposed to be leaf-structures — 
for example the thorns in some species of Rudus and Smilax, the 
ridges in the stems of Urtica gracilis, Mentha crispa and Leptandra 
Virginica. 
For these reasons the wings are, it seems to me, rather to be 
regarded as lateral-vertical expansions of the stem than as “ decur- 
rent leaf-margins.”’ 
PHOTOTROPISM 
To determine the action of the plant towards light a growing 
shoot was fastened in a dark chamber illuminated from one side 
only. After fourteen days there was found to be a decided photo- 
