LEAF-ARCHITECTURE AS ILLUMINATED BY A STUDY OF PTERIDOPHYTA. 685 



those of Campbell on the cotyledons of G. dichotoma* But there the arrested 

 apex is shown expanded, not still circinate as in the case of G. fulva. 



The young plants thus provide all the morphological essentials for the formation 

 of the most elaborate leaves of the genus, viz. a scorpioid sympodial branching, and 

 a possible arrest of the apex, which may be periodical above any of the apparently 

 opposite, paired pinnae. Unlimited development along these lines, but with varying 

 proportions, will account for the various types of leaf seen in the genus. 



Matoninese. 

 The very striking leaf-architecture of Matonia has been repeatedly discussed, for 

 instance by DiELsf and by Tansley.J The latter collected young plants on the Malay 



d 



FlO. 19, a-d. —Juvenile leaves of Matonia peetinata. a, though detached and broken, was the cotyledon 

 of the plant, b. The drawings were made from specimens collected by Dr Lang on the Malay 

 Peninsula, and kindly lent for the purpose. ( x 4.) 



Peninsula, and depicted them. Though his observations help materially to a 

 solution, they do not provide an exhaustive account. Dr Lang, who travelled with 

 Mr Tansley, has kindly lent me his preparations of young plants of Matonia, and a 

 more consecutive series illustrating the structure of the juvenile leaves can now be 

 given. But it appears that the young plants and prothalli are only rarely met with 

 in their native habitat. 



The prothallus was still attached to the youngest specimens. The simplest form 

 of juvenile leaf is that shown in fig. 19, a. It was originally attached to the plant 

 (J>), but broke away in the preparation, clearing, and staining, and it had already 

 been broken across the middle. There is, however, no doubt that it was the coty- 

 ledon, and that it was unbranched. The venation is a scorpioid sympodium, with 



* L.c, pi. x, figs. 55-57. 



t Natiirl. Pflanzenfam., i, 4, p. 343. 



| Ann. o/Bot., 1905, p. 447. 



