Notes . 
28 
General Conclusions. 
The chief conclusion arrived at from a study of these new seeds relates to the 
light which they throw on the habit of members of the Pteridospermeae. At present 
we are only acquainted with one genus, Medullosa, in regard to the manner in which 
the seeds were borne. 
In neither L . Kidstoni nor L. Sinclairi is there any direct evidence as to the 
type of sterile frond with which they were associated, but the general morphology of 
the branched axes bearing the seeds affords a valuable clue to the habit of the sterile 
fronds. These axes are regarded as portions of a compound frond with reduced 
lamina. In the case of L. Kidsioni the long rachis-like structures present many 
points of morphological similarity to the fronds of the Sphenopteris type. In 
L. Sinclairi the frond, had it possessed a lamina, would in all probability be placed 
in the same genus. Thus there is every reason to suppose that the sterile foliage 
associated with these seeds was of the Sphenopteris type. 
This conclusion is supported by the recent attribution of the seed L . Lomaxi to 
Lyginodendron , a stem known beyond doubt to have possessed fronds of this nature. 
There is thus strong evidence that these new species, which in the morphology 
of their seed-bearing axes approach so closely to the foliar organs of Lyginodendron , 
and, in their seeds, agree so well with L. Lomaxi , were borne by stems either of 
Lyginodendron itself, or of some closely related member of the same family possessing 
the Sphenopteris form of sterile foliage. 
There is, therefore, to be found in these specimens the first definite clue to the habit 
of the Lyginodendreae with regard to the manner in which the female fructification 
was borne. If this conclusion is correct, we may picture these plants as bearing, in 
addition to numerous highly-compound fronds of the Sphenopteris type, Others in 
which the lamina was wholly or partially reduced, and in which the ultimate branches 
terminated in seeds, with or without a ‘ cupular ’ investment. 
In the lax arrangement of the fructification, the Pteridospermeae must have 
presented a striking contrast in habit to the members of most of the other great 
Palaeozoic groups, in which compact strobili were for the most part conspicuous and 
dominant types of sporangial aggregation. Among living plants, almost the only 
analogue is to be found in the female sporophyll of Cycas. 
E. A. NEWELL ARBER. 
Trinity College, Cambridge. 
