216 MR. W. ARCHER ON THE MINUTE STRUCTURE AND 
thereto. Ifthe plant be viewed under a low power, the two contours—the broadly rounded 
and the deep conical—come into view nearly simultaneously, and we have the curious and 
contradictory appearance of the joints having, as it were, ¿wo bottoms; and this is what gives 
rise to the puzzling appearance alluded to. Now the pits, with their accompanying 
remarkable knob-like stoppers, are seen to occur in the nearly transverse septum over the 
seeming conical base. If there were a conical base of the upper joint, passing down into 
and introverting the tip of the joint immediately below, how could the knob or stopper 
of the upper end of the lower joint get past the barrier, and become opposed, on its own 
pit, to that at the bottom of the upper joint? Without any opening or passage, mani- 
festly it could not be so deposited in its proper place. 
The curious appearance of the introversion of the upper end of the lower joint might, 
indeed, possibly meet its explanation by assuming an interspace, from this ordinary 
aspect of a bluntly triangular or conical figure, between the two joints; somewhat 
comparable to the very differently shaped interspace between the mutually introverted 
ends of several forms of Spirogyra, but in the present plant, indeed, only one (the lower) 
joint being introverted. But even if this were true, it would not explain the pair of 
directly opposed “ knobs ;" for one would be at the base of the upper joint, and the other 
must then be in an “ intercellular space," and therefore outside the cavity of the lower 
joint, thus offering really no explanation, and in truth presenting a puzzle just as dificult 
of solution as ever. 
The fact is that the apparent introversion of the upper end of the lower joint by the 
lower end of the upper joint projecting downwards into it, an interpretation which 
naturally occurs to every one on first looking at this plant, is illusory. 
So illusory is it, indeed, that Harvey himself, in describing his Ballia Brunonia, 
directly falls into the error, and quite misapprehends the true state of affairs *. He 
actually describes the structure, speaking of the joints of the rachis, thus :—“ Articulus 
singulus apice concavus, basi convexus, superior in inferiorem insertus, e cellula unica 
formatus, sacculam endochrome includens;" and afterwards he says, “ each joint is 
concave at its superior end, convex at its inferior, having thus a somewhat cordate 
figure, the convex end being inserted into the joint immediately below it, while the 
coneave receives in like manner the one above. These joints consist of a single cellule, 
and contain а bag of colouring matter which is collapsed in a dry state." Аз will be 
seen, the true structure is quite the reverse of Harvey's description ; whilst he is alto- 
gether silent as regards the pits and stoppers, whatever be their value or significance. 
Nor does it appear that subsequent authors had detected the fallacy or noticed these 
curious ** stoppers.” l 
The true explanation is, that the lower end of each joint is in fact deeply cleft or 
forked laterally—that is, forming two wedge-shaped subdivisions ; and these latter are 
tapered off towards each front, more or less conically, and then truncato-rotund, or 
rounded off subhemispherically. То some extent it might not be altogether inaptly 
compared to the top of a bishop's mitre. 
* Harvey, “ Description of Ballia, a new genus of Alge,” in Hooker’s Journal of Botany, 1840, p. 190. 
