7o 
Lady Isabel Browne. 
of the Marattiaceae seems to he largely governed by the fact that 
their leaves are usually not so highly compound, and their sporangia 
are exannulate and eusporangiate. The exannulate eusporangiate 
condition is probably primitive; nevertheless the existence of 
Palaeozoic Marattiaceae can no longer be regarded as established. 
The Psaronieae, the forms most probably related to the Marattiaceae, 
seem to have been too complex anatomically to have given rise to 
the simplest forms of each phylum. For instance, Dr. Hallier 
derives the Psilotaceae directly from the Marattiaceae, regarding 
their synangia as strictly homologous. Even if, as seems not 
unlikely, the Psilotaceae are somewhat reduced, the origin of the 
protostele locally present in them from a Marattiaceous vascular 
system seems quite untenable. The Lycopodiaceae are regarded by 
Dr. Hallier as derived from Marattiaceous forms allied to the 
Psilotaceae (17). Anatomically it is most unlikely that the 
Lycopodiaceae should be derived from the Marattiaceae ; from this 
point of view an affinity between the Lycopodiaceae and Psilotaceae 
has much to recommend it, but as pointed out above, the absence 
of a sporangiophore in the former makes it doubtful whether the 
affinity is close. Dr. Hallier holds that the numerous sporangia of 
a fern-frond have been, in the Lycopodiaceae, reduced to one; 
Pleuromeia is regarded by him as a primitive Lycopod retaining the 
numerous sporangia of its fern-like ancestor. But not only is this 
genus merely of Mesozoic age, but this or any other interpretation 
of its fructification is very doubtful. The incompletely septate 
sporangium of Isoetes is regarded as a synangium homologous with 
the synangium of the Marattiaceae. The discovery of a form 
probably allied to Isoetes (i.e., the Rhaetic Lycostrobus Scotti ) with 
an apparently septate microsporangium favours this suggestion, but 
even so the single non-septate sporangium appears to be the oldest 
type among the Lycopodiales. Dr. Hallier recognizes the affinity 
between the older Equisetales and the Sphenophyllales ; he derives 
them both from the Marattiaceae. Here again the anatomy of 
Equisetum and still more that of Sphenophyllum absolutely forbids 
such an origin. This scheme of classification seems very unnatural; 
one of its defects is that Dr. Hallier assumes, to judge from his 
diagram, that the strobilus originated but once in the vegetable 
kingdom. But among the Strobiliferae he includes the Cycado- 
filices, which we now know not to have been strobiloid; the 
cones of their descendants, the Cycads, therefore presumably 
originated separately from, and more recently than those of, the 
