364 Gibson. — On Siliceous Deposit in the 
generally consists of a simple coating of thin irregular plates 
over the parenchyma forming the cortical wall of the lacuna. 
S. atroviridis, Spr. 
The features of the deposit in this species are precisely 
similar to those of S. Martensii, var. compacta . 
S. erythropus, Spr. ; S. bakeriana, Bailey ; and S. steno- 
phylla, A. Br. 
A thin deposit occurs in these species on the innermost 
cell-layer of the cortex, penetrating between its constituent 
cells. 
S. involvens, Spr. 
The cortex of this species shows considerable variation 
from the type condition. The epidermis encloses several 
layers of sclerotized elongated cells with minute intercellular 
spaces, showing a gradual transition to the loosely arranged 
inner-layer and finally to what corresponds to the trabecular 
tissue. In fact, the entire conjunctive tissue outside the 
pericycle and endodermis cannot be differentiated into layers 
such as one sees in other forms. The intercellular spaces 
are numerous and large and either filled or lined by a large 
amount of siliceous deposit. The silica is most abundant 
in the middle layers, but can be traced almost to the 
epidermal layer outwards, and to the endoderm inwards. 
In the latter case the deposit begins in the angles formed 
by the juxtaposition of the cylindrical cells, of which the 
cortex is uniformly composed. 
S. gracilis, Moore. 
The deposit in this species resembles in all respects that 
in 5. Lobbii. 
S. flabellata, Spr. 
The silica is confined to the minute intercellular spaces 
between the two innermost layers of the cortex and to the 
depressions between the free cells of the superficial layer 
facing the lacuna. 
