MARATTIACEAE 511 



fissions in Kaulfussia supports this vtew (Fig. 281 a-e, lower series). Thus 

 the apparently aberrant genus may be brought into line with the rest. It 

 will be seen later that this spreading 

 of the sori over an enlarged leaf- 

 surface has its parallels among the 

 Leptosporangiate Ferns also. 



The normal arrangement with 

 one row of sori on either side of 

 the midrib corresponds to what is 

 frequently seen in the fossils which 

 are referred to this affinity : as 

 examples Asterotheca, Scolecopteris, 

 and Ptychocarpus may be quoted 

 (Fig. 282, also Fig. 288 A). In 

 all of these, though the pinnules 

 are small, the arrangement of the 

 sori is on the same plan. But FlG 28o 



among the Fern-like plants of the 



Diagrammatic view of a trunk of a tern from the 

 PalaeOZOlC age many Other arransre- Coal > showing above the external cortex with petiolar 



scars (Caulopteris), and below the woody cylinder 

 meiltS OCCUr which appear tO have with scars corresponding to the foliar strands, and 



their sclerotic sheaths (Pty 'chop tens). Reduced to 

 no near Correlative among living J natural size. (After Zeiller). 



Ferns. 



The examples here chosen from among the fossils are those in which 

 there is at present no reason to doubt the homosporous Fern-character. 

 It is possible that some of them may ultimately be shown to be Seed- 



FIG. 281. 



a, 6, c (above), Danaea data, Smith. a = a fertile pinna with many normal sori: the 

 arrow indicates an abnormal fission ; b, c, show more numerous abnormal fissions, resulting 

 in irregularly formed sori, distributed over a slightly enlarged leaf-surface. X2. a, c 

 (below), sori of Kaulfussia at-sculifolia, Blume, showing states of partial or complete" 



ahstriction. 



Plants, and the sori to represent groups of pollen-sacs. But even if they 

 were, the structural similarities would remain, and they would then only 

 strengthen the opinion that the Pteridosperms had an ultimate origin in 

 a Fern-like ancestry. 



