298 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
at the edge of the cap. Commelina coelestis also forms tricho- 
blasts. 
Eriocaulaceae. Lachnocaulon Michauxii is remarkable for its 
resemblance to Lycopodium in the longitudinal division of the 
trichoblasts, and the consequent occurrence of the root-hairs in 
groups of 2, 3, or 4 at the ends of the hairless epidermal cells. 
The trichoblasts first appear as distal segments, generally of 
lenticular form, often embracing less than the entire width of 
the cell-rows in which they are formed (pi. 18, fig. 74). They 
were seen to arise at about 40 cells from the apex in one actively 
growing root of considerable size. The trichoblasts divide 
longitudinally very shortly after formation. Commonly a single 
division suffices, but often this is followed by further division 
(pi. 18, fig. 75). Occasionally one of the half trichoblasts 
divides transversely (pi. 18, fig. 76). The inner part of the 
trichoblast spreads out, both transversely and longitudinally, 
jutting under the ends of contiguous atrichomic cells. In the 
fixed tissue the trichomes are sharply differentiated from the 
remaining elements by the extreme shortness as well as by the 
peculiar form of their bases (pi. 18, fig. 77). Paepalanthus 
flavidulus exhibits the same peculiarities. Trichoblasts were 
found which had undergone both transverse and longitudinal 
division, with the result that four trichomes were formed in 
a group. The trichoblasts originate as distal segments. This 
statement holds also for Eriocaulon septangulare. It is to be 
noted that as regards the origin of the trichoblasts, the 
Eriocaulaceae agree with the Glumiflorae, and that, as far as it 
goes, this evidence supports Engler’s view that the Farinosae 
are derived from the Glumiflorae. 
Xyridaceae. Xyris flexuosa var . pus ilia : figure 79 (plate 18) repre¬ 
sents a portion of the young fixed epidermal tissue, in which 
the distinction of trichomic and atrichomic cells is well seen. 
The hair emerges laterally as in several cases heretofore noted. 
Figure 78 (plate 18) shows a younger stage in profile. Xyris 
caroliniana: in figure 80 (plate 18) trichoblasts are seen in the 
region of increasing elongation of the root. The contrast 
between hair-cells and intervening prismatic cells is shown in 
figure 81 (plate 18). 
