BENEDICT: GENERA OF THE FERN TRIBE VITTARIEAE 185 
similar to venation patterns found in other tribes. For example, 
the twin net type of venation, as in Polytaenium, which is not 
uncommon in other tribes of ferns, cannot be used as a basis for 
comparison but must be considered as of independent origin in 
each tribe. 
2. SIGNIFICANCE OF MONOGRAMMA 
The significance of Monogramma is a difficult problem to solve. 
On the assumption of a dichotomously veined leaf as generally 
primitive for ferns, first stated by Goebel, I believe, Monogramma 
and the whole tribe Vittarieae might be considered as the affirma- 
tive exception to the rule. But here a difficulty presents itself, 
since the other genera appear usually to pass through a dichoto- 
mous stage following the uninervate beginning. The uninervate 
type must then either be recognized as more primitive than the 
dichotomous type or else as a derived condition in this tribe. 
Study of the first leaves of other simple-leaved ferns is needed. 
The marginal position of the sporangia in M. dareicarpa and 
M. graminea is in agreement with Bower’s suggestion as to the 
probable primitive condition for ferns. It is interesting to note 
here that the attainment of the dorsal position in the other genera 
is a direct consequence of the branching of the veins, since all or 
any of the veins appear to be potentially sporangiferous. Bower 
assumes, however, a primitively divided type with only marginal 
or submarginal sori, the dorsal position having been attained by 
the migration of the sori. In this hypothetical primitive type the 
sporangia are assumed to have been definitely localized in sori, 
not as in the present case in lines of indeterminate length. The 
present tribe is interesting in this respect because it offers an 
instance of the development of an approach to a soral condition 
(as in Anetium) from an indeterminate development of lines of 
sporangia. 
But whatever the phylogenetic significance of Monogramma, 
its position, at least as regards two of its species, as the simplest of 
known vascular plants can scarcely be questioned. The leaf 
structure is analogous in its simplicity to that of the lycopods 
generally. The stele, it may be noted, as far as I have been able 
to determine from sections of soaked herbarium material, is a very 
