of Fossil Plants of the Coal-Measures. 319 
vascular cylinder of the Lepidodendron referred to above. 
In the latter example the cells are less densely packed within 
the vessels than in the former one ; hence they retain more of 
their primitive spherical form. 
In my memoir ix 1 , I figured and described a selection from 
a very large number of macrospores belonging to a species 
of Lycopodiaceous strobilus, and the endosporal cavities 
of these spores are more or less filled with cells of various 
sizes and conditions. In many instances these cells are free; 
in others they are combined into a parenchymatous tissue. 
In most of the examples the cells are seen to be located 
within an inner membrane, c , which I assume is the endosporal 
membrane lining the very thick exosporium. Two of these 
macrospores are represented in Figs. 15 and 16, the former 
being enlarged 57° diameters, and the latter 250 diameters. 
The thick exosporium, a , of these spores is always clothed 
externally by numerous simple or branched hair-like append- 
ages, b. Both the above examples contain numerous cells, 
the two specimens representing sufficiently closely the two 
extremes of the average sizes to which these cells attain. 
Those of Fig. 15 have a mean diameter of about of an 
inch. In Fig. 1 6 two or three, as at c, are larger than the 
rest, being g in diameter, but most of the cells in this speci- 
men have a maximum diameter of about tsVtt °f an inch. 
In my memoir x 2 , 1 represented similar cells in the interior 
of the spores to which, in a previous memoir, I gave the 
provisional name of Zygosporites, and in Plate 18, Figs. 42 
and 45 of the same memoir, similar cells were shown, occupy- 
ing the macrospores of my Strobilus Traquairia. In Plate 
17, Figs. 25 and 31 (loc. cit.), similar cells are seen in several 
species of the curious reproductive bodies, belonging to some, 
as yet, unknown plants, and to which bodies I have assigned 
the provisional name of Sporocarpan. I have not thought it 
necessary to reproduce all these anomalous forms in the 
present memoir. These aspects are approximately represented 
1 Phil. Trans. Part ii. p. 345 et seq ., PI. 23, Figs. 65, 66, 66 a, 66 B, 66 c. 
2 Phil. Trans. Part ii. 1880, PI. 19, Fig. 55. 
