ORIGIN AND NATURE OF THE MUCILAGE IN THE CACTI l6l 
mucilage cells not only in the cacti but also in the mallows, Tilia, Sterculia, 
tragacanth (Astragalus gummifer Labill), etc., have been comprehended. 
Kiitzing (through Wigand, 1863) as early as 1851 saw the lamination in 
tragacanth, but had an entirely incorrect idea of the origin of the mucilage 
cells, regarding them as a fungus. Mohl in 1857 (also through Wigand) 
explained the appearance of gum tragacanth as due to the centripetal 
deorganization of the cell membranes and their change into the gum, a view 
which certain later observers (Karsten, Schleiden, Wigand) adopted. 
Cramer in 1855 saw the lamination of the mucilage cells in the cacti. Wi- 
gand (1863, p. 149) described the collapsed protoplasmic utricle as a more 
or less evident trace of an ill-defined cavity, with radiating arms ("radia- 
tions") penetrating the mucilage-content in a manner analogous to pore- 
canals, without properly apprehending the significance of these details. 
Walliczek (1893) correctly described in a topographical sense the structure 
of the cell as a whole, but erred, as I think, with Longo (1896) in regarding 
the mucilage in Epiphyllum, etc., as granular, the granules (so regarded 
by Walliczek) being merely cavities (Longo) due to dehydration by alcohol, 
in which medium Walliczek examined his material. His description of 
the mucilage cells in Opuntia Tuna appears to be incorrect, since "mucilage 
strands stretched in an irregular network through the lumen" do not occur. 
It would seem that he misinterpreted one of the bizarre conditions caused 
by rapid hydration in which there are numerous delicate and meshed strands 
of protoplasm passing out radially through the mucilage to the cell wall. 
This appearance I have often seen, and is caused by the pinching of the 
protoplasm by mutually appressed masses of mucilage. Under such con- 
ditions the protoplasm is squeezed into lacunated layers, thus producing 
the meshed appearance described by Walliczek. 
Concerning the mode of origin of the mucilage there are diametrically 
opposed views, namely: (a) that the mucilage is secreted within the pro- 
toplasm (Lauterbach, iS8g, fide Walliczek, p. 267) or in extreme form that 
the mucilage cells have a "plasma gommeux, qui vie et vegete a la maniere 
du plasma des cellules ordinaires" (Trecul, 1862, and restated in 1875); 
and (b) that the mucilage is some form or product of the cell wall. The 
latter view appears in different forms. 
Wigand thought that the mucilage arises by a deorganization of an 
already present secondarily much thickened cell wall. De Bary (1884, 
p. 144), following Wigand (whom he cites), and apparently depending on 
his descriptions, regarded the mass of mucilage in the cells of mallows, cacti, 
and laurels as having the "structure of a very thick, abundantly and deli- 
cately stratified cell wall," and that it is . . . nothing more than a cell 
wall which has thickened [italics minej strongly at the expense of the central 
cavity." 
Walliczek (p. 268) thought that the mucilage is laid down on the primary 
membrane as a secondary thickening, in the formation of which the primary 
