180 PHOTO-MICROGRAPHS. 
braced apart by stellate cells having long arms, 
the extremities of which meet in the interior. 
This structure may be seen in Canna. The pith 
of the rush and of numerous water-plants is also 
made up of stellate cells. 
The difference in the structure of Exvogens and 
Endogens is illustrated in Plate XI. In the one 
case (Exogens, Fig. 1), the interior of the stem 
is made up of a loose cellular structure, pith ; 
next to this comes the woody part of the stem, 
containing the fbro-vascular bundles; and outside 
of all, the cells making up the bark. In the En- 
dogens, on the contrary, there is no distinct wood, 
pith, and bark, and the fibro-vascular bundles are 
seattered through the stem. These are seen in 
cross-section in Fig. 2, but a longitudinal sec- 
tion is required to show their structure, and, 
indeed, many sections from various plants will 
be necessary to illustrate this in a satisfactory 
manner. 
In Plate X., Fig. 1, we have a picture which 
might easily pass for a pattern of lace-work, 
and one might wonder at the odd conceit of the 
person who designed it in introducing a figure 
of a skull into every second scallop. This de- 
sign, however, is made by Dame Nature, as the 
photo-micrograph is from a thin transverse sec- 
tion of the leaf of Pampas-grass. 
