LEPIDODENDKEAE. 239 



The walls of the sporangia are unusually thin, being formed of a single 

 layer of palisade-like cells ; the isolated microspores (?) which they contain 

 are globular ; the edges of their pyramidal apices are winged, and are pro- 

 duced at the basal extremity into spreading triangular teeth (Fig. 25 C). It 

 was remarked above that Williamson 1 has found fragments of cones in the 

 plant-petrifaction of Burntisland, along with branches and stems of his Lepi- 

 dophloios brevifolius, and that he assigns them to the vegetative remains 

 as their fructifications. The microsporangia were only met with in one 

 instance along with the other parts, and then they occupied as usual the 

 basal portions of the cones. Their spores are large and clothed all round 

 with a close array of curved filiform membranous processes. In one figure 2 

 Williamson gives a tangential section, which passes through the upper part 

 of the strobilus where the microspores are concealed, and shows the rhombic 

 transverse sections of the sporophylls with wings on both sides exceedingly 

 well. These are provided on the under side with a wing-like process 

 answering to the median bundle, and on the upper side bear the sporangium, 

 the narrow insertion being plainly seen in the middle of the lamina. The 

 sporangium has its wall formed of one layer of cells, and is filled inside 

 with a great number of small microspores united together in fours. 



The only form which remains to be mentioned is an imperfectly known 

 strobilus, which Williamson 3 has described from materials found near Old- 

 ham and Halifax ; here the macrospores are the only spores that are 

 known, and they are marked by sundry peculiarities. That this fossil 

 belongs to Lepidodendreae is rendered very probable by the spiral not 

 verticillate position of its sporophylls, and by the presence of only one 

 sporangium over the transverse section of each scale, as the tangential 

 section shows 4 . The structure of the axis is not to be seen in the speci- 

 mens which have been figured ; but I find from a preparation, for which I 

 am indebted to Mr. Cash, that it resembles that of Lepidodendron Har- 

 courtii. The macrospores have the usual tetrahedral form, the edges of the 

 sides of the pyramids project strongly, and the base is convex; but they 

 are furnished with a hollow bladder-like appendage, which runs across the 

 middle of the basal surface like a curved tube, and evidently represents an 

 organ analogous with the air-sacj of the pollen of the pine. If the spore is 

 cut through in a direction parallel to its length, it appears of course as a 

 broad one-sided wing. Transverse sections pass through it twice at its two 

 extremities, and then there appear to be two hollow bladder-like appen- 

 dages opposite to one another. Williamson also states that he has found a 

 large number of minute cells inside the spores, but he says nothing precise 

 about their nature. I have certainly seen these cells in the preparation 



1 Williamson (1), III, t. 44. a Williamson (1), in, t. 44, f. 24. 3 Williamson (1), IX, 



t. 22. 4 Williamson (1), IX, t. 22, f. 55. 



