45 8 Bower . — Studies in the Phytogeny of the Filicales. 
will be noticed that of the two indusial lips that on the abaxial (lower) side 
at first develops the stronger, and the whole sorus comes to be tilted over 
to the adaxial side. The same is also the case, though in less degree, in 
Dicksonia (Fig. u) and in Odontosoria (see below, Fig. 17). In later stages 
this inequality is made up, and even reversed, so that in the final state the 
sorus in all of these Ferns appears to be shifted distinctly to the lower side, 
while the upper flaps of the successive sori fuse laterally to form a con- 
tinuous flange (compare Kunze, c Farrenkrauter/ Taf. XLI, c). This is 
particularly well shown in Goebel’s Fig. 10, ‘Flora/ 1912, p. 47, and he 
describes the nature of the sorus of Sciccoloma thus : ‘ That which has been 
described as the “ scarcely modified leaf-margin ” is composed of the con- 
tiguous outer flaps of a two-flapped indusium. These outer flaps are larger 
than the inner. Still one sees the several sori clearly limited by a seam-like 
swelling, so that there can be no doubt of the interpretation thus given/ &c. 
The facts of development above given fully demonstrate the correctness of 
this conclusion, while comparison of other species, as well as with species 
of Davallia y further strengthen the position. Still the sori themselves 
remain distinct, each with its own separate receptacle, and with the ‘ inner ’ 
or lower flap of the indusium separate also for each individual sorus. 
Owing to the fact that my Jamaican material presented an incomplete 
series of stages for developmental study, a full account cannot be given at 
present for Saccoloma. But enough has been seen from rather advanced 
conditions of the sori to make it certain that a one-sided gradation of origin 
of the sporangia is present. The most advanced sporangia are those nearest 
to the lower or ‘ inner * flap of the indusium, while passing from these 
towards the upper or ‘ outer ' flaps, which are fused as a false ‘ leaf-margin ’, 
a succession of younger sporangia is seen. The sorus has, in fact, under- 
gone just such a modification as might have been anticipated in a type of 
marginal origin, with equal development on both sides, which had become 
phyletically shifted to the lower surface of the leaf, with consequent unequal 
development of its sides. Moreover the biological advantage of such pro- 
tection is too obvious to need detailed explanation. 
As regards the dermal appendages, broad brown scales are found in Sacco- 
loma elegans, together with simple hairs. They all fall away, however, from 
the leaves at an early stage, and in the mature state the surfaces of the lamina 
and the petiole are quite bare. Thus as regards the anatomy Saccoloma 
appears to be closely linked with the relatively primitive Thyrsopteris , which 
had itself arrived at a condition advanced in anatomical complexity when 
compared with Cibotium Barometz. In point of dermal appendages it is 
advanced relatively to both of them ; also in its partial merging of the sori, 
and in their one-sided, gradate sequence of sporangia. The sum of these 
characters will give it a higher phyletic position than the Dicksonieae, though 
the anatomy will leave little doubt of its natural affinity with this family. 
