274. Prof. H. Karsten on the Formation, 
I have repeatedly observed, for example, in the wood of Cin- 
chona, 
Among the large cells of the vertically elongated parenchyma 
of the stem of Philodendron, some scattered rounded cells are 
met with almost completely filled with a large erystallme mass 
of oxalate of lime. In these cells also, when occurring in a mass 
of cork-tissue, some young cells are seen to originate between 
the crystalline mass and the parent cell, which, after having 
acquired their full dimensions, have a cellulose composition, and 
ultimately become converted into cork. These cells so entirely 
surround the crystalline mass that it appears to be enclosed 
within an envelope of small irregularly shaped cork-cells inter- 
vening between it and the parent cell-wall (fig. 2 4). 
Besides these kinds of cells, which all contribute to the cica- 
trization of the cut surface by the formation of cork, two other 
elementary organs are encountered in the tissue of Philodendron; 
in these no cell-development takes place, but they become ab- 
sorbed within the layer of cork-cells. The first of such organs 
are the series of cells, united with fibres and filled with raphides, 
which are found dispersed in the parenchyma of the bark and 
of the medulla, and which in other Aroidez contain a milky 
juice. The second kind are the branching fibrous cells found 
only in the cortical tissue. Both these structures are, in all 
probability, principally concerned in the process of secretion— 
an opinion which I expressed suppositively, in my ‘ Disserta- 
tion,’ with regard to the thickened secondary membrane; I also 
specially mentioned the absorption of the fibrous cells of the 
bark, in my Memoirs on the Palms and on the China-barks (Die 
Vegetationsorgane der Palmen, 1847, p. 53, and Die med. 
Chinarinden Neu-Granada’s, 1858). 
These fibrous cortical cells of the Philodendron have a remark- 
ably ramified form, giving off from each side of the upper and 
lower extremities of the parallelopipedal and horizontally ex- 
tended cells two very long and thin branches, which le free in 
the comparatively wide intercellular spaces, and end in pointed 
closed extremities. These long branches, standing out at right 
angles from the cell, are not produced until after this has at- 
tained its full size; and soon after the outgrowth of these pro- 
cesses the entire cell-wall proceeds to increase in thickness. It 
can indeed be distinctly made out that these cortical cells, as 
well as the lacteal vessels, here occupied by raphides, originate 
from cells, and not from intercellular spaces lined with cell- 
material. 
In my paper on tannic acid (Monatsbericht der Berl. Akad. 
der Wissenschaften; 1857) I described the lacteal vessels of 
Colocasia, Dieffenbachia, and other Aroidez through which a 
ile 
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