478 Tans ley and Lulham. — A Study of the 
phyllopodium with a right and a left lateral. A microtome series of 
the top of the petiole and base of the frond, however, reveals a clear 
dichotomy of the single petiolar strand into two equal trunks, one of 
which (that belonging to the central lobe) increases in size somewhat, 
and sends off a branch nearly at right angles, which becomes the midrib 
of the left-hand lobe. This behaviour of the vascular strands certainly 
suggests a primary dichotomy, one of the members of which sends off* 
a single branch from its base. 
Plant B (Fig. 2) has a small frond with apparently a primary dichotomy, 
one of whose members remains small, while the other undergoes a secondary 
dichotomy. The larger frond, on the other hand, if we may judge from 
the course of the vascular strands, has a middle lobe, from the base 
of which arise two laterals, each of which branches, whether dichotomously 
or monopodially it is hard to decide. This frond, assuming the laterals to 
dichotomize, may be regarded as a sort of prototype of the adult frond. 
Plant C (Fig. 3) has both its fronds, and Plant D (Fig. 4) two of its 
three fronds, clearly showing a primary dichotomy, while the subsequent 
branching, especially in C, appears to be very largely dichotomous. 
Fig. 5 ( a detached leaf of Plant E) shows an unusual type of leaf. 
Fig. 6 (another leaf from E) returns to the type of the larger frond of B 
(Fig. 2), i. e. a trifid leaf. Here, however, all three lobes are branched, 
partly at least dichotomously, the middle one most extensively. 
Plant F (Fig. 7) has all its leaves of this trifid type, and the branching 
of each lobe is for the most part monopodial, though a tendency to 
dichotomy is still observable in some cases. In the weaker fronds of 
the starved plants mentioned above, this trifid character is the rule ; but 
in one case at least (Fig. 8) there is a clear primary dichotomy with no 
middle member, and each branch apparently forks again, three of the 
four resulting members branching monopodially. The stronger fronds 
of the starved plants are simply feeble expressions of the adult type. 
(Cf. Fig. 9.) 
The adult type of frond in this species is quite unique among the 
Ferns. e The long petiole branches to the right and left, giving off lateral 
members from the upper faces of its two recurved arms in a scorpioid 
manner ’ (Seward, ’ 99 , p. 175). It is well illustrated by Seward (’ 99 , p. 176, 
Fig. 1). In all the fronds we have ourselves seen there is a middle 
‘ pinna ’ arising from the angle of the dichotomy. This is commonly the 
longest of all the pinnae. 
The following solution of the problem as to the real nature of this 
curiously branched frond is suggested. The primary branching of the 
frond is assumed to be dichotomous. Many of the leaves of the young 
plants are difficult or impossible to interpret as monopodially branched, 
and a primary dichotomy appears to be the simplest explanation of the 
