480 Tansley and Lulham. — A Study of the 
of Gleichenia , e. g. G. circinata , speluncae , and elongata , exhibit inter- 
mediate forms in which the bud of the main rachis grows more strongly 
than the primary forks, and the successive forkings of the rachis appear 
as pinnae, while G. Boryi actually shows a typical pinnate structure 
of the whole frond, the main rachis itself ending in a £ pinna.’ 
We are inclined to regard the frond of Matonia pectinata as having 
also taken origin from a primitive dichotomous type, but in another 
direction. The middle lobe or bud in the angle of the primary fork has 
here been at once limited in growth so that it forms a pinna, while the 
primary forks dichotomized repeatedly, the upper member of each successive 
fork forming a pinna, while the lower branched again. Thus the Matonia- 
frond became moulded into a fan-shaped structure with a power of peripheral 
growth, while the ordinary Fern-frond acquired a pinnate structure retaining 
a power of terminal growth. Here again certain species of Gleichenia 
furnish evidence of intermediate stages in such a process of evolution. 
G. Jlabellata , Br., G. Cunning hand, Hew, and G. quadripartita , Hk., show 
the relevant phenomena. Seward (’99, p. 192, Fig. 7) has already noticed 
the ‘superficial resemblance’ of the frond of G. Cunninghami to that 
of Matonia pectinata. In the frond of the former species which he figures 
there is no middle bud evident, but the primary forks of the frond (which 
bear pinnules from their base) fork again close to their base, and each 
of the four secondary members at once forks again. The three upper 
members on each side so produced become simple pinnae, undergoing no 
further branching, but the lowest (peripheral) member on each side 
dichotomizes once more. This already gives us an indication of what 
has taken place in Matonia pectinata. G. Jlabellata sometimes produces 
fronds (Plate XXXI, Fig. 10) which are even closer to the Matonia-type, 
for here only the lower members of the secondary forks dichotomize, and 
the bases of the primary forks are bare of pinnules, while a median bud 
is present, though it has become adherent to one of the primary forks 1 . 
If this bud were developed into a pinna (a condition which is sometimes 
realized in G. cryptocarpa , Hk., though in that species the frond is more 
complicated and less compact), and the peripheral dichotomizing were 
carried further, we should have the type of the adult Matonia pectinata. 
In G. quadripartita , Hk., the arrest of the branching of the frond after 
the second dichotomy is characteristic, as the specific name indicates, 
but the lower branch on each side here also sometimes branches again, 
as in the frond of G. Jlabellata figured. 
Fig. 9 shows a frond of Matonia from one of the starved plants 
alluded to above. The secondary dichotomy has occurred on the left, 
1 On the hypothesis suggested in the footnote on p. 479 this middle bud would represent the 
arrested inner branch of the first dichotomy of the left-hand member of the primary fork. Its 
position here would then be more primitive than when it occupies the actual angle of the fork, as in 
most Gleichenias. 
