Brown: Woops FOR MICROSCOPIC STUDY 143 
they may be few in number or may compose nearly or quite 100 
per cent of the prosenchyma. In some cases (Robinia), the purple 
reacting lamellae of fibers may function as reserve material, and 
be more or less completely dissolved in the growing season (Schel- 
lenberg, ’05; Griiss, ’96). In this connection, twigs of Acer 
rubrum L., Cercis canadensis L., and Robinia Pseudo-Acacia L., 
gathered in winter condition, sectioned, and treated with zinc 
chlor-iodide, make favorable material for study. A number of 
distinctive propention are exhibited by such fibers: 

a. Hyg ——Mucilagi layers readily take up water, 
swell without see sabes selabiou, and shrink correspondingly on 
; B 

0 5 10 
R 15 20 25 u T 
Fic. 4. Abbé camera drawings of a laminated fiber of Xylosma hawatiense 
Seem. in cross-section. © mut after desiccation. B, after treatment with water. 1 
yers have swollen, but the mucilaginous layers (G) more than the ligno-cellulose 
outer portion (ZL). The pode pits (P) come into alignment after soaking. One 
of the pits remains permanently in connection. T, tangential direction. R, radi 
direction. 
drying. If cross-sections 15-30 » in thickness are mounted on a 
slide in water, then dehydrated by flowing absolute alcohol be- 
neath the coverslip, the mucilaginous layers may be observed to 
shrink greatly, in the majority of cases, drawing away from the 
