32 MINNESOTA BOTANICAL STUDIES. 
similar that no change is noticeable in passing from one to the 
other. In the lamina proper, however, the pith cells branch 
more and the rows of cells have a more meandering course, 
and there is more anastomosing. The intercellular jelly is de- 
veloped here more than elsewhere in the plant. Due to this 
and some to the branching of the cell rows the blade is much 
thicker than the stipe. 
The cortex and epidermis are similar to those of the stipe. 
The crowding growth of the conceptacles disarranges the order- 
liness of the cell arrangement in the cortex and epidermis. 
Cross and longitudinal sections of the lamina resemble those of 
the stalk closely, except for the differences just mentioned, and 
for the conceptacles (/7g. 3 shows a partial cross-section of a 
lamina). 
The growing poit.—In the tip of the maturer laminz no 
definite growing point can be found. There still is some growth 
and cell division going on here in the outer cortical cells, and 
in a mature lamina this is probably the youngest and tenderest 
portion. It is here that the lamina begins to burst when placed 
in fresh water. Even at the sinus between the lobes of the 
lamina no growing point can be found in older lamine. This 
is the place where the growing point once was. But the growth 
seems to have stopped here first and continues for a time longer 
toward the ends of the lobes. 
If a young frond is examined, one in which there is as yet 
no difference between stem and blade, a slight notch or dimple 
is visible at the top. This notch deepens in older fronds, and 
if a section is made through the somewhat flattened stipe, par- 
allel with the flat surface and through the axis of the frond, a 
large apical cell is seen at the base of the sinus (P/. X., Figs. 
5, 16), This apical cell is an epidermal cell. It is in the 
shape of a truncated pyramid, with the truncated end to the top 
or pointing outward. The apical cell is two or three times as 
large as the other epidermal cells, and is otherwise markedly 
distinguished by great richness and granularity of contents, and 
by the absence of chromatophores. The adjacent cells share 
these characteristics to a less degree. They show a diminution 
in the granularity of the protoplasm, and color grains begin to 
appear in all but the latest cutoff. 
The apical cell, as seen in vertical section, cuts off daughter 
cells in succession, a lateral, then a basal, and then a lateral 
