IX MARATTIACEA£—ISOETACEyE 273 



cell divides repeatedly, but apparently without any definite 

 order, and the division of the spores follows in the usual way. 

 From the cells about the archesporium tapetal cells arc cut off, 

 but these do not disappear, as Goebel ^ asserts, but persist until the 

 sporangium is mature. The growth is greater upon the outer 

 side, which is strongly convex, while the inner face is nearly flat. 

 A section of the nearly full-grown sporangium (Fig. 143, C) 

 shows that the wall upon the outer side is much thicker, 

 and is composed for the most part of three layers of cells, 

 of which the outer in the ripe sporangium have their outer 

 walls strongly thickened. The top of the sporangium and the 

 inner wall are composed of but one layer of cells (exclusive of 

 the tapetum), which are flat and more delicate than those upon 

 the outer side. Near the top on its outer side is a transverse 

 line of cells with thickened darker walls, which project some- 

 what above the level of the others. This is the annulus or 

 ring, and resembles closely that of Osniundn. Lining the wall 

 is a layer of very large thin-walled cells which form the tapetum. 

 This in Angiopteris remains intact until the spores are divided. 

 Whether it disappears before the dehiscence of the sporangium 

 was not determined. The contents of these cells, which are 

 very much distended, and evidently actively concerned in the 

 growth of the forming spores, contain very few granules, but 

 are multinucleate in many cases. Whether this condition is 

 due to a coalescence of originally separate cells, or what seems 

 more likely, arises simply from nuclear division in the young 

 tapetal cells, without the formation of cell walls, was not 

 decided. The young spore tetrads, at this time, are embedded 

 in an apparently structureless mucilaginous matter, which stains 

 uniformly with Bismarck-brown. This apparently is secreted 

 by the tapetal cells for the nourishment of the spores. 



Classification of MarattiacecB 



The living forms are divisible into three families : — 



I. Angiopterideae, with the single genus Angiopteris, and 

 probably only one extremely variable species, A. evecta (Hoffm), 

 which occurs throughout the Eastern tropics. 



II. Marattieai, with two genera, Marattia and Kaiilfussiar 



1 Goebel (3), 1881, p. 684. 

 ^ Kaulfiissia is sometimes made the type of a separate family. 



T 



