STEMS, LEAVES, AND BUDS. 
47 
furrows, similar to what in art is called ‘‘ en vermeil.” The 
different crystalline forms of oxalate of lime, as found in the 
Cactacew, are stated. The author found, in 100 parts of the 
perfectly dry vegetable substance of plants, 85.57 of oxalate 
of lime, 5.75 humic acid, 7.79 vegetable fibre, and 0.92 loss. 
The Cactacece frequently contain carbonate of lime, besides 
oxalate of lime, and that often in perfectly formed “ rhom- 
bohedrons,” as, for instance, in the Cerens triangularis. 
The opinion of the author, that young cells form themselves 
from a cytoblast, and then make their appearance after the 
resorption of the mother cell, he endeavours to prove by ob- 
servations made on very young bulbs of Georgina^ where two 
cells develop themselves from a cytoblast in one mother celL 
The author then proceeds to treat of the external layer 
of the bark, the epidermis, and the outer bark. He says, 
besides the ordinary bark-parenchyma, we meet with, in the 
one-year-old shoots, beneath the epidermis, in almost all 
plants, particularly of those which convert themselves into 
wood, a more or less thick layer of peculiar cells, the walls of 
which are in a different chemico-physical state to those of 
the ordinary cell-membrane of the parenchyma. This tissue 
contains most water when in its youngest state, and is almost 
identical with vegetable mucus ; it hardens subsequently through 
the loss of water. The cells at first have thin walls, but 
thicken in their gradual development, but owing to the gela- 
tinous quality of these walls, it was impossible for the author 
to distinguish layers ; but pores presented themselves, which 
may here be observed to particular advantage. The various 
changes of this cellular tissue are given. The commencement 
of the formation of the outer bark, or rather of the formation 
of the cellular layer, consists, according to the author, in the 
fact, that a darkish, yellow-brown, granular mucus matter col- 
lects itself in a certain locality in some of the epidermic cells. 
This substance gradually increases, till it bursts the sidewalls 
of the cells, and raises the upper walls, which are connected 
together in a continued membrane, whilst the lower walls 
remain firmly combined with the layer of bark situated be- 
neath. In the third place, he treats of the wood. There is 
439 
