meristems of Ferns as a Phylogenetic Study. 351 
developments appear to have been frequent on the Ferns of 
earlier geological periods 1 , though they are rare on living 
species. Dissection of the bases of the leaves of this plant 
shows that the profusely branched ‘ Aphlebiae ’ are inserted 
above the extreme base, and, like the normal pinnae, alter- 
nately along the marginal lines or wings : they vary in 
number, two, three, or four being found on each leaf: their 
branching is irregular at the base, but higher up they produce 
alternate branches of a higher order (pinnules), which are 
inserted on the reduced marginal wings. The higher branches 
widen out into thin, meagre expansions, which correspond in 
general conformation to the normal pinnae, but are of a much 
more reduced type. 
Comparing their microscopic structure with that of the 
normal pinnae, it is seen that they show the same characters 
but on a reduced scale; e.g. the normal pinna is five layers 
of cells in thickness, the aphlebia only three to four ; while 
stomata and intercellular spaces are present in both : thus the 
comparison of these aphlebiae to ‘filmy’ Ferns is based on 
slender grounds. All the facts above adduced point to the 
conclusion that the c aphlebiae ’ of Hemitelia capensis are 
nothing more than peculiarly developed basal pinnae, and 
when the fact is added that on one of the Edinburgh plants 
a pinna was found showing intermediate characters between 
the normal and the aphlebiae, this conclusion is greatly 
strengthened. But what circumstances they are which have 
led to so strange a development of certain pinnae, and the 
question whether in all the cases in which such growths have 
been described for fossil forms a like explanation is possible, 
must remain for the present undecided. 
Material could not be obtained for working the actual 
development of the aphlebiae. 
From Prantl’s account of the Schizaeaceae 2 it would appear 
that these observations were made. Compare also Hofmeister, Higher Crypto- 
gamia, notes on pp. 212, 243. 
1 Solms-Laubach, Palaeophytologie, p. 136. 
2 Schizaeaceae, p. 4. Compare his Plate VII., Figs. 109, no, hi ; Plate VIII, 
Fig. 133 . 
