Bower.—Studies in the Phytogeny of the Filicales. VII . 17 
receptacle in related Ferns is liable to be tilted. In Lindsay a linearis 
(Fig. 13, iii) it is deflected to the lower surface ; in Saccoloma elegans 
and Odontoloma retnsa 1 it is tilted towards the upper. In Dictyoxiphium it 
is still more strongly tilted towards the upper surface, so that, in the absence 
Fig. 15. Transverse section of a sporophyll of Dictyoxiphiumpanamense. ( x 18.) 
of the upper indusium, its surface appears almost as a continuation of the 
upper surface of the leaf. Beneath the receptacle runs a vascular commis¬ 
sure, as in Lindsaya or Pteris ) while it bears numerous sporangia produced 
in ‘ mixed ’ succession. They are long-stalked when mature, and after 
dehiscence the sporangial head breaks away, leaving the persistent three- 
rowed stalk. 
These facts, stated provisionally until more suitable material can be 
had, support generally the reference of Dictyoxiphium to a relation with 
Lindsaya and with the Pterids. The interest in comparison with the latter 
lies in the point that while in Dictyoxiphium the upper indusium is abortive, 
in the Pterids (as will be shown below) it is the lower indusium that 
is reduced, and disappears in the more advanced types. In Dictyoxiphium 
the sorus shows signs of spreading to the upper leaf-surface ; in certain 
of the Pterids it tends to spread to the lower surface ; and in Acrostichum 
it may occupy a large part, or even the whole of that surface. Such 
changes in the originally marginal sorus are similar in kind. They differ in 
relating the one to the upper, the other to the lower surface of the leaf. 
Saccoloma . 
A similar though less complete lateral linking of sori into a marginal 
series has been described in Saccoloma elegans . 2 Here again the origin of 
the receptacle has been found to be marginal, while there is a one-sided 
gradation of sporangia upon the receptacle. In fact it is easy to recognize 
this condition as a modification of the Dicksonioid type, with closely related 
sporangia shifted to the lower surface. But Saccoloma is greatly in advance, 
anatomically, upon IAndsaya ; this suggests that their soral states may have 
resulted from parallel development rather than from phyletic unity. It 
bears broad brown dermal scales upon its stock. 
It is now possible to give some more exact account of the stelar 
condition of Saccoloma elegans , Klf., than has yet appeared. It is based 
upon material collected in Jamaica, which had been handed over to 
1 Studies, III, PI. XXXIII, Figs. 16, 17. 
2 Goebel, Flora, Bd. cv (1912), p. 46, Fig. 10. Also Bower, Studies, III, Ann. of Bot., 
vol. xxvii, p. 457. 
C 
