516 PROFESSOR W. C. WILLIAMSON ON THE ORGANIZATION 
that it is an integral part of the organism. Fig. 55 is also one of the larger specimens, 
its disk having also a diameter of '006. Each of its radial arms terminates in an 
unbranched, semi-clavate extremity, hut I doubt if tins is normal. It appears rather 
to be a result of imperfect preservation. The real importance of this specimen is 
seen in the large and very distinct cells, c, located within the cavity of the disk. 
Other examples have afforded similar, though less strongly-marked indications that 
such cells belong to the organism, and were doubtless developed, as in other spores, 
within the interior of the membrane, b, of fig. 56. 
I have met with several examples of the apparently distinct form represented by 
fig. 54, and as all the sections exhibit the same aspect, having a pentagonal or 
hexagonal disk, with a diameter of about '0018, and five or six long, slender arms, 
the length of each arm being about equal to the entire diameter of the central sphere, 
this object is probably distinct from the other species described. I would therefore 
designate figs. 51, 53, 55, and 56 Zygosporites brevipes, and fig. 54, Z. longipes. 
I have given to these objects the name of Zygosporites, without meaning that they 
are actually zygospores, though there is much reason for adopting such a conclusion. 
M. Charles Brongniart, of Paris, informs me that he has found similar objects 
amongst the discoveries of M. Grand- Eury, at St. Etienne, and that he refers them 
to living types of Desmiclese. I am not prepared to advance thus far. Had true 
Desmidese existed in the carboniferous strata, I see no reason why their extremely 
characteristic bilateral cells should not have been preserved as readily as other cellular 
tissues which my cabinet contains. Having many scores of examples of these Zygos¬ 
porites, the plants to which they belonged must have been common in the locality in 
which they grew; but I have not discovered the slightest trace of a Desmicl in these 
deposits. 
Figs. 58 and 59 represent sections of an organism of which I have met with several 
examples in two slides from Halifax, for which I am indebted to Messrs. Spencer and 
Bjnns. Fig. 58 is a transverse section through the centre of one of these objects, 
enlarged 1260 diameters. Its actual length is '0042. Fig. 59 is a more tangential 
section of another specimen about '0041 in length. In both specimens the wall of the 
organism exhibits numerous points at which it is projected outwardly into small, 
hollow prominences, and which appear to have subdivided extremities like the radial 
arms of the Zygosporites. Indeed, these objects only appear to me to differ from 
Zygosporites in their oblong form, and in the smaller size and greater numbers of 
their peripheral appendages. Such being the case they may be named Zygosporites (?) 
oblongus. 
In my memoir, Part VIII., I described and figured (Plate 9, fig. 44 and 46, g, g) 
sections of brandies of Dacloxylons, in which pairs of vascular bundles passed outwards 
through the woody zone. These specimens left me under the impression that these 
paired bundles proceeded to leaves, and not to branches. Fig. 60 represents part of 
a transverse section of a branch obtained by Mr. Spencer from the marine Ganister 
