274 LYCOPODIALES [CH. 



The diagrammatic sketch, fig. 218, B, shows the relation of the 

 integument to the sporophyll and sporangium, the outline of 

 the latter being indicated by a broken line. The columnar wall 

 of the sporangium (fig. 218, A, 6) forms a closed beak within 

 the micropylar crevice, and in the interior of the sporangial 

 cavity the slightly shrivelled membrane, a, represents the single 

 megaspore ; traces of the aborted sister-cells of the megaspore are 

 occasionally met with. Scott describes a specimen in which the 

 megaspore is filled with tissue agreeing in appearance with the 

 prothallus in a megaspore of Isoetes or Selaginella ; no un- 

 doubted archegonia or female organs have been discovered, nor 

 has any spore been found containing an embryo. 



The axis of L. Lomaxi has a medullated stele constructed 

 on the same plan as that of some species of Lepidodendron and 

 Lepidostrobus ; the vascular bundles supplying the sporophylls 

 pass obliquely upwards and outwards from the stele, St, fig. 

 218, B, and bend slightly downward just before entering the 

 pedicel of a sporophyll. 



Dr Scott has also described a strobilus containing micro- 

 sporangia partially enclosed by a rudimentary integument. It 

 is, however, of considerable interest to find a partial develop- 

 ment in the case of a male flower of an integumentary outgrowth, 

 which it would seem could only be of real functional importance 

 in the female shoot. 



It is important to notice that specimens of a second species 

 of Lepidocarpon, L. Wildianum, are recorded from Lower 

 Carboniferous beds of Scotland, a fact which points to a con- 

 siderable antiquity for this seed-bearing Lycopodiaceous type^. 



The most important question to consider in regard to 

 Lepidocarpon is — are we justified in applying to the integu- 

 mented sporangia the term seed ? The megaspore was not 

 set free as it is in recent Pteridophytes, such as Azolla and 

 other genera with which Lepidocarpon may be compared ; it 

 was on the other hand retained in the sporangium, as may 

 sometimes happen even in recent species of Selaginella (cf 

 fig. 131, D). Moreover, the megaspore is characterised by a thin 



1 Seott (01) 314. 



