400 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
so far been obtained. In certain specimens of Stephanospermum, 
which has some points of resemblance to 7rigonocarpon, the preser- 
vation is so complete as to show the pollen grains contained in the 
pollen chamber of the seed; the cell group, probably representing 
the antheridium, is clearly seen in the pollen grains. 
Regarding the anatomy of the Medulloseze (a family name pro- 
visionally taken as synonymous with Neuropteridez), it may be 
noted that the structure of the Permian species is much more com- 
plex. The elaboration consists essentially in the differentiation of 
a central and a peripheral system of steles, the peripheral system 
sometimes forming a continuous, or nearly continuous, ring. As 
the secondary growth of the external steles was in some forms 
much greater on the outer than on the inner side, a certain resem- 
blance to the stems of Cycadacez with medullary bundles is notice- 
able, accentuated in the largest stems of J/. stellata by the appear- 
ance of extrafascicular zones of wood and bast inclosing the whole 
stelar system. Some authors, notably Mr. Worsdell, have laid great 
stress on these resemblances, which lead them to place the Medul- 
loseee on the line of descent of the Cycads. Personally, I have been 
unable to convince myself that the stem of the Cycadaceze admits 
of an interpretation on “ polystelic ” lines, though on other grounds 
the affinity suggested has much in its favor. 
While we have in the Permian Medullosee striking examples of the 
extreme complexity which this type of stem was capable of assuming, 
Sutclifia insignis, a plant recently discovered in the Lower Coal 
Measures of Lancashire, carries us back to a type of structure prob- 
ably more primitive than had previously been known in this family. 
The stem has a central stele of great size, without pith, the solid 
centripetal wood consisting of pitted tracheides interspersed with 
bands of parenchyma. From the principal stele, large vascular 
strands, the meristeles or subsidiary steles, are detached, which divide 
up and fuse with one another, ultimately giving rise to the leaf-trace 
bundles, a large number of which enter the leaf bases. The petiolar 
bundles are concentric, resembling those of Seward’s Rachiopteris 
Williamsoni, which was no doubt the petiole of another species of 
Sutclifiia. In the specimen investigated, secondary growth in thick- 
ness was only just beginning. In habit and various structural details 
the plant agrees with a Medullosa; it shows a near approach .to mono- 
stelic structure, for the single central cylinder forms a dominant 
feature in the vascular system, while the meristeles effect the tran- 
sition to the leaf traces. The concentric bundles constitute a more 
Fern-like character than is known elsewhere among the Medullosez. 
The plant is of considerable interest, as indicating the probable 
derivation of the Medullosean stem from a simple protostelic type, 
such as occurs in //eterangium among the Lyginodendre. 
