MODE OF GROWTH ОЕ BALLIA CALLITRICHA. 221 
one, their apices rounded. Thus this cortical stratum of cells somewhat resembles a 
kind of pleurenchymatous or prosenchymatous tissue. As our examination is carried 
from below upwards, this cortical: stratum becomes more confined to the margins, 
leaving more or less of the stem-joints bare at the middle, until by-and-by it dis- 
appears altogether. 
Here and there, with patience, one can probably meet with a profile view of the 
point whence the cells of this pleurenchymatoid cortical stratum is given off from 
one of the multitudinous branches which stick about most confusedly in all directions. 
In Mr. Moseley’s plant these seem scarcely ever themselves to become branched, but 
form only indefinitely long “© confervoid” filaments. Whilst, as mentioned, the septa 
of the vertical cortical cells are oblique, those of the branches given off therefrom are 
ever transverse; but, like those of the former, every septum here, again, has its minute 
pair of pits and stoppers. Only occasionally one can get a satisfactory profile view of the 
place of ramification; and it can be seen that this process here too is sometimes 
brought about by the intervention of a “ramification-cell.”” But this does not maintain 
the same figure as that of a rachis-cell as above described. Here, however, as 
there, an oblique, sometimes curved, septum is formed just under one of the ordinary 
oblique septa of a cortical cell, reaching from a point, say, about a quarter of the length 
of the septum from the outer wall to a short distance down the lateral margin of the 
cortical cell. Thus a minor cell is cut off, forming in this view a scalene triangle, two 
of its angles being acute, one obtuse. Soon the upper portion of its free side (being in 
_ fact a portion of the original outer margin of the cortical cell itself) grows out laterally, 
and, by apical growth and repeated subdivision of its apical cell, gives rise to one of the 
long accessory filaments, every septum, as mentioned, having its pair of minute pits and 
stoppers. The cells gradually diminish in size ; in other words, the filaments gradually 
taper. The apical cell, when full-grown, is conical, its apex acuminate; but until then 
the apical cell is bluntly rounded. Whether, on the occasion of the giving-off of these 
lateral branches а ramification-cell is always formed, ог whether they sometimes branch 
off without that preliminary by a simple outgrowth, merely standing off, as they some- 
times seem to do, like a thumb to a glove, I could not decide. 
So much for the ramifications of the cortical cells and the mode in which they them- 
selves coat the principal rachises. Within one of these, so coated, one can see, by 
focusing down, shimmering through the investing cortical layer, the great pits and 
stoppers of the largest size, as well as the contours of the joints, with their ramification- 
cells giving off subsidiary rachises. "These latter project through the cortical stratum 
of cells; and by far the greater number of these subsidiary branches themselves are 
naked. At a first glance, the question might propound itself, why do the investing 
fibres “тап up" only a few of the subsidiary branches, and not all? why are they so 
much more dense low down, as compared with the upper portions of the stems and such 
rachises as they do invest? 
This leads to the inquiry, What is the origin of the cortical cells (we have seen the 
origin from them of their lateral branches), and what their relation to what may, as 
before, be called the “ Ballia proper"? And this is just an inquiry to which it is very 
.. SECOND SERIES.— BOTANY, VOL. I. 21 
