389 
This curious plant, as already stated, was hollow, with the walls 
consisting of three or four, or possibly more, layers of cells. The 
epidermal cells are markedly separable into two kinds: first, narrow 
bands of three or four rows of thin-walled cells which are two to 
four times longer than broad, separated by broad areas or bands 
ten or twelve cells wide, of short irregularly quadrangular cells. 
In figure 1 a, a, represents the bands of narrow cells, and b, b, the 
short irregular cells. Under the microscope the two kinds of cells 
divide the surface longitudinally in very clearly mark parallel lines. 
The stomata are the most remarkable feature about this plant. 
As may be seen by the drawing, the guardian cells are quite irreg- 
ular in shape and appear to vary in number from four to six, the 
most frequent number being five.* The opening is in all cases 
large and in some instances appears even larger than either of its 
guardian cells. It is difficult to see how so large an orifice could 
be completely closed by them. 
The stomata, it will be observed, are confined to the broad 
bands of irregular cells, and are also arranged in longitudinal rows, 
those next to the bands of long cells being numerous, while in the 
central row they are scattered, there being only about one-third as 
Many as in the others. The orifice between the guardian cells is 
approximately circular. The guardian cells are themselves ar- 
Fanged in a more or less regularly circular manner, their shape de- 
Pending on the number present. When there are only four they 
are rectangular with rounded outer sides; when there are five or 
More they are keystone-shaped, or broadly wedge-shaped. 
Iam at the present time unable to suggest any satisfactory re- 
lationship, either living or fossil, for this anomalous plant. The 
first thought when seeing the numerous fragmentary stems 
throughout the clay mass, and finding that they are hollow, is that 
they belong to Aguisetum. But on examining large numbers of 
fragments, not a single joint with the characteristic teeth could be 
detected, and moreover the stomata are entirely different. It is of 
Course well known that the stomata of living Aguise¢um have two 
; atk as pidermal 
*In figure 1 the guardian cells appear to be in the same plane as the e 
“ig They are of course below them, but the lines of the overlying epidermal cells 
have not been drawn in, so that there may be less confusion in following their eee 
* Figures 2 and 3, much enlarged views of single stomata, make the real condi 
tion plain, 
