develops within the sporangium and fills the sporangium 
nearly completely, although a central cavity sometimes 
remains. 
In 1914, Kidston (6) described a small strobilus of 
Lepidocarpon westfalicum trom the upper Carboniferous 
of Staffordshire. This is a particularly instructive spec- 
imen because the strobilus is said to contain a large num- 
ber of ‘‘ripened’’ seeds borne spirally upon an axis. The 
seeds are quite small attaining a length of only 2 to3 mm. 
and a thickness of slightly less. We have found in Iowa 
a single strobilus of Lepidocarpon lomaai in which the 
seeds are much larger, as a matter of fact attaining a 
length of nearly 4.5 mm. A comparison of isolated spec- 
imens of L. /omaxi with those attached in the strobilus 
has shown clearly that those not yet shed from the cone 
are immature rather than ripened. The average length of 
those which have been shed is nearly 6 mm. The histo- 
logical detail preserved in the megaspores which are still 
enclosed in their sporangia and sporophyll never demon- 
strates the advanced degree of differentiation encounter- 
ed in the isolated specimens. The diameter of the strobilus 
of Lepidocarpon westfalicum Kidston is approximately 
1.5cm. On the individual seeds there is a smooth pit at 
the basal end which marks the place where the sporan- 
gium was attached distally upon the sporophyll. 
In 1936, Miss Reed (10) reported on the nature of 
isolated specimens of Lepidocarpon. A single vascular 
strand traverses the full length of the sporophyll. The 
sporangial wall is described as having two layers, each 
averaging three cells in thickness. Both layers, however, 
are composed of thick-walled isodiametric cells and at 
first appearance look much alike, the epidermis being 
only slightly differentiated from the hypodermis. Accord- 
ing to her description the sporangium does not have a 
hypodermis with the distinct palisade appearance of 
[ 87 ] 
