THE 
AMERICAN NATURALIST. 
VoL. x11. — WAY, 1878. — No. 5. 
HAIRS AND GLANDULAR HAIRS OF PLANTS, THEIR 
FORMS AND USES. 
BY*PROF. W. J. BEAL. 
OMMON in green-houses is a plant called Ageratum mexi- 
canum, which is grown chiefly for its light-blue heads of 
flowers which are valuable for bouquets. The stems and frame- 
work of the leaves are slightly rough on account of large num- 
_ bers of hair-like projections along the entire surface. A small 
_ fragment placed under 
and delicate objects as 
follows: 
The greater number 
of these consists of from 
five to twenty cells of ` 
_ Curved hairs on Ageratum mexicanum.} 
end. Each hair or chain of cells is curved more or less, often 
into a complete ring, always towards the top of the plant. The 
end cell is blunt or rounded at the tip. Scattered among these- 
are occasionally seen sharp-pointed hairs which are straight and 
much more slender. Still less frequently may be seen larger and 
stouter projections, like Fig. 4, in which there are two rows of 
-` The degree to which these figures are magnified is not given because of consid- 
_ erable uncertainty in most cases, The objects were all drawn by Mr. W. S. Holds- 
VOL. XII,~—NO. V. 
