West. — A Contribution to the Study of the Marattiaceae. 387 
back in the successively produced leaves, till it is obvious at their first 
origin at the base of the foliar gap. 
Lotsy ( 47 , p. 681) briefly states, with reference to Marattia sambucina , 
that ‘ Der Stamm hat eine weniger komplizierte Dictyostele als Angiopteris\ 
Campbell ( 20 ), as a result of his investigations upon the vascular 
anatomy of young sporophytes of Marattia Douglasii and Marattia 
sambucina , brings this genus into line with Danaea and Kaulfussia by 
maintaining that the solid strand which occurs at the base of the stem is 
composed of the united traces of the earlier leaves. This botanist also 
describes (20, pp. 191-3) the anatomy of the stem of a small adventitiously 
formed plant of Marattia alata ; his description of the stelar system of 
this species agrees essentially with that given for Marattia fraxinea by 
Farmer and Hill (l.c.). 
The most recent and complete account of the development of the stele 
in this genus, however, was published by Charles ( 23 ), who had the great 
advantage of working with abundant material of Marattia alata . At the 
base of the young sporeling this observer finds (1. c., p. 97) a protostele from 
which the transition to a solenostele takes place suddenly and without the 
intervention of a distinct medullated monostelic stage. Later, a medullary 
strand arises, and at first behaves like the commissural strand in the young 
sporophyte of Danaea , but as the leaf-traces become more crowded, the 
medullary strand divides into a number of branches, which join the stelar 
cylinder above the leaf-gaps. Eventually, however, a second cylinder is 
produced by anastomosing and branching of the medullary strands (1. c., 
p. 92, Fig. 3). The main root-supply joins the external system, the 
medullary system having only a few small roots. 
The model represented in Text-figs. 17 and 18 was built up from a 
series of transverse sections of the caudex of an adult plant of Marattia 
Cooperi , Mre., the base of which had unfortunately completely decayed 
away. A transverse section of the existing basal region of this specimen 
showed a ring of strap-shaped bundles surrounding a single central bundle 
(Text-fig. 19), whilst a similar section taken just below the apex of the same 
plant showed two concentric zones of strands (Text-fig. 18). The region of 
the stelar system at which the transition between these two conditions takes 
place is represented in this model, from a study of which it is seen that the 
stem-stele of this plant is made up of a simple dictyostelic cylinder with 
extremely large foliar gaps (cp. Farmer and Hill, 1 . c., p. 379) and an internal 
accessory system which at first consists of a single commissural strand, 
a short branch from which assists in closing the foliar gap. Subsequently, 
however, further elaboration of the internal conducting system takes place 
by branching and anastomosing of the original commissural strand, whereby 
an internal vascular cylinder is produced (Text-fig. 18). Only a single 
compensating strand (Text-fig. 18, comp. si) leaves this inner cylinder to 
assist in closing the gap formed in the outer cylinder by the departure of 
