166 STEWART: MUCILAGE FORMATION IN THE CACTI 
23. Walliczek, H. Studien iiber die Membranschleime vegetativer 
Organe. Jahrb. Wiss. Bot. 25: 209-277. pl. 11-13. 1893. 
24. Wigand, A. Ueber die Deorganisation der Pflanzenzelle, insbeson- 
dere iiber die physiologishce Bedeutung von Gummi und Harz. 
Jahrb. Wiss. Bot. 3: 115-182. pl. 5-7. 1863. 
Explanation of plate 8 
Fic. 1. Cell from a section of a very young stem of Rhipsalis rhombea showing 
cytoplasm about the periphery = pean starch grains and nucleus. Magnifica- 
tion about 1,900 diameters. 
Fic. 2. Cell adjoining that shown in Fic. 1, showing the hint stage in the for- 
mation of a mucilage cell. Nucleus and nucleole are much enlarged, cell is filled 
eters. 

with cytoplasm, no starch is present. gnification about 1,900 diam 
Fic. 3. Cell aoe a — gee a oe oven of Rhipsalis rhombea. A peek 
nucleus and nucl ,asin Fic. 2. A narrow 
border of mucilage like : a thin film lies abebieon the ‘atl ‘wail and the peering 
Magnification 1,300 diameters. 
Fic. 4. Mucilage cell from the ovary eines of a bud of Rhipsalis Houlletiana. . 
The cytoplasm is compressed to a small mass in the center of the cell, its organizatio 
lost, but the nucleus still ee jt mucilage fills the space between ip 
cell wall and the cytopla Magnification 600 diameters. 
Fic eae ot tri a flower bud of Rhipsalis pachyptera. The cyto- 
plasm lies in the central part of the cell and is very much compressed. A few starch 
oa still persist, ie nucleus and nucleole are disintegrated. Magnification 600 
diameters. 
‘ Section of a wall between a mucilage cell and two adjoining cells in 
flower ee of Ete genes pachyptera, showing the middle lamella. Magni onntatses 
I,100 diamete: 
Fic. 7. Picea of a section from a flower bud of Rhipsalis pachyptera 
showing the zonation in a mucilage cell. The darker central portion is cytoplasm, 
the striations in the mucilage being nearly parallel to it. 
