298 
PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
vasculaires isoles entourant la moelle et choir partiraient les cordons foliaires. Dans 
ce type on ne troaverait ni l’axe completement vasculaire du L. Rhodumnense ni le 
cylindre ligneux continu du L. Harcourtii.” Surely this plant fulfils the chief require¬ 
ments of M. Renault’s third type c, his definition of which I have just quoted. 
But even were it otherwise, the example of the Lyginodendron Oldhamium described 
in my memoir, Part IV., shows that a medullary sheath may be continuous in a young 
state (see Memoir IV., Plate 22, fig. 2) and yet be broken up into widely separated 
vascular bundles (idem, fig. 3) through advancing age and growth. In these respects 
the structure of the medullary cylinder in Sigillaria elegcms and spinulosa presents 
almost a fac-simile of the conditions seen in the larger stems of my Lyginodendron 
Oldhamium. 
Calamostachys B inn eyana. 
Much as has been already accomplished in the investigation of this interesting 
fruit, we are far from knowing its entire history. I am now able however to fill 
up two lacunae in that history. We have hitherto been ignorant of the nature and 
position of the organic union of the sporangia to the sporangiophores; but I found in 
the cabinet of Mr. Cash, of Halifax, a transverse section that gives the required infor¬ 
mation. A portion of this section is shown in fig. 23, k being a part of the outer cortex 
of the strobilus. At v, v, are two sporangiophores, one of which retains its peripheral, 
expanded disk at v , and a marginal portion of the other is seen at v". The disk con¬ 
sists of a mass of parenchyma, amongst the cells of which an extension of the bundle of 
spiral cells that passes along the peduncle of the sporangiophore, is seen prolonged to¬ 
wards the margin of the disk; as the bundle approaches this margin its cells multiply 
as is the case with the similar structures in the sporangiophores of the recent Equiseta, 
as well as in other very different structures— e.g., the terminations of the hair-like 
emergences of the Droserce. The peripheral surface of the disk appears to have 
been composed of a layer of oblong cells, which are planted perpendicularly to it. 
At v" and v" we see that each sporangium is not connected with the peltate end of 
the sporangiophore by the entire base of the former, as is the case with the living 
Equiseta, but by a very narrow neck of cellular tissue attached to a point a little 
within the extreme overhanging margin of the sporangiophore; the remainder of the 
base of the sporangium being entirely free, as is seen at u. 
My second discovery is a still more important one. All the examples of this 
Calamostachys hitherto described, possess but one kind of spore. But some years ago 
I found a fragment, still in my cabinet, in which the sporangia were filled with spores 
of about three times the diameter of those with which I was familiar. My immediate 
conviction was that these were macrospores—but the specimen being so fragmentary, 
and there being no microspores connected with it, I durst not rely upon its apparent 
indications since it was possible that it might only represent some transitional state 
of the common form of spore. The correctness of my surmise is however established 
