124 Bower.— Is Eusporangiate or Leptosporangiate 
family as no more than a provisional suggestion : he is careful 
to state 1 that in none of these has the sporangium itself been 
seen, but at most the indusium of the sorus, or the receptacle 
without sporangia. 
Passing on to specimens of the carboniferous period, where 
the microscopic details can be seen in sections, evidence is 
found of the structure of the sporangia being more complex 
than that of the Leptosporangiate Ferns. This is the case 
in the sporangia figured by Williamson 2 , for in these, traces 
of a second series of cells are found within the external layer 
of the wall, a character which is absent in the mature 
Leptosporangiate sporangium. Prof. Williamson has, with 
great liberality, shown me those of his sections of coal nodules 
which exhibit Fern sporangia, and the comparatively small 
number of these shows how rarely they are preserved. I was 
struck in looking over these specimens by their great 
uniformity of type, and have selected a few for detailed 
drawing (Figs. 1-4). In examining these it is to be borne in 
mind that the sections pass in irregular directions through 
the sporangia, but still the similarity is unmistakeable : in each 
case the superficial layer of cells has thickened and firm cell- 
walls, but the individual cells are of very irregular size and 
shape ; no definite ring-like annulus can be traced. Within 
the outer layer are to be found in each case more or less 
distinct traces of internal cells (z, z), which do not constitute a 
regular and continuous layer, but only a partial internal 
sheath ; at some points a simple line may be seen (as in 
Fig. 4. x), without any distinct layer of cells ; this will be 
referred to subsequently. The number of spores in the 
single sporangium is relatively large, as may be judged from 
the sporangium shown in Fig. 4, where more than seventy 
are seen in the single section, and the total number in 
the sporangium must have been much larger. None of the 
sections show clearly the mode of insertion, and the sporangia 
1 Stur, Die Carbonflora, 1885, p. 235. 
2 Phil. Trans., vol. 167, Part I, on the organization of the Fossil Plants of the 
Coal Measures, Part VIII, PI. 7, Figs. 25-30. 
