344 The Botanical Gazette. [June, 
difficult to see the real structure of the tip region. The tip 
may be seen, however, by directly crushing the frond. This 
removes too many of the branchlets or disturbs too much 
their relative position. The application of boiling water to 
dissolve a large amount of the gelatinous substance allows us 
to examine the tip with every axial filament and branch in its 
natural position. 
The tip of the plant is never conical. The number of axial 
filaments and their branches is so great even in the youngest 
plants examined, that extreme care is necessary to distin- 
guish those occupying the exact tip. It is certain that no 
single filament at the tip exceeds the others in size, and that 
there are present at the extreme tip of the plant a number of 
filaments almost exactly alike (fig. 11). The smallest num- 
ber of filaments possible to trace to the very tip was three 
(fig. 11), the lower filaments and the final branchlets of each 
filament having been gradually removed by gently crushing 
the plant which had been treated with hot water. 
_ Turning now to the adult frond below the tip, we find that 
it is made up of distinct axial and cortical layers. Each of 
these layers is made up of branching filaments. In the ax!s 
the filaments are made up of long narrow cells, from 30 
125p in length, containing small colorless chromatophores 
(fig. 11, a, 4). The walls marking the cell divisions of these 
threads are so far apart (often 125) as to have made Agardhs 
statement® a most natural one. ‘‘The filaments proceeding 
downwards are inarticulate and cylindrical; those growing 
upwards are articulated, and more or less contracted at the 
dissepiments.” These central cells divide at irregular inte™ 
cell wall, 
branches which may proceed undivided in the central region 
the perfect fascicle. The ‘“‘downward growing” arms tur : 
the periphery as much as do the ‘“upward growin e” arms, 4 
—— ho Piery as Muchas do the “upward. growing ETT 
® Harvey, Nereis Bor. Am. 134. 
