a 
688 KupFER: ANATOMY AND PHYSIOLOGY 
The whip- hairs, too, seem to differ from the types of Vesque 
in that they are also, as a rule, bicollateral. They are thus ap- 
parently homologous with the gland-hairs. The early condition 
of the two kinds of hairs is very similar, the only difference being 
that the whip-hairs are from the beginning devoid of chlorophyll. 
In the adult condition, however, they are entirely separated from 
each other. The enormously enlarged end-cells have walls so 
highly thickened that the cell-lumen is almost obliterated (/ 5). 
The developing whip-hairs are cutinized almost from the start. 
When fully formed they are also uniformly covered with cutin, 
but there is a stage in their growth in which the base only of the 
end-cells is surrounded by a collar of cutin, while the thickened 
Hairs of Baccharis genistelloides. Fic. 4. Gland-hair. Fic. 5. Two whip-haits. 
Fic. 6, a, 6, Developing whip-hairs. 
cellulose wall of the upper part shows prominently above and 
through it (/ 6 @ and b). Probably the cell in its period of hy- 
pertrophy breaks through its cutin covering, which is reéstablished 
after growth has ceased. The two whip-hairs often fail to 
develop simultaneously, so that a pair is frequently found, one 
of which is still in its prime, while the other consists of only 
shriveled empty cells. As far as has been determined, new hairs 
of either kind are not developed much below 5-6 cm. from the 
tip. As some also drop entirely off, the hairs on the older por 
tions are very scattered and frequently consist of only the shriveled 
cells. 
