SCHIZAEACEAE 



547 



)bably they had originally a more complex annulus than those of the 

 isent day. 



The development of the sporangium follows in its main features the 

 lal Fern-type, each being referable to a single parent-cell, with rectangular 

 It is specially noted by Prantl, 1 that in all the Schizaeaceae the 

 >t segment-wall extends from the outer to the inner periclinal wall of 

 lis cell : such segmentation is a feature characteristic of the more robust 

 js of Fern-sporangium (Fig. 305). This is followed by two other anticlinal 

 ivisions, as seen in section, and then comes the 

 riclinal division which separates the cap-cell from 

 archesporium. The former gives rise to the 

 reater part of the sporangial wall, while the lower 

 rments complete the wall, and form the short 

 ilk. In the archesporium the usual tapetum and 

 >rogenous group are formed : the latter consists, 

 >wever, of a larger number of spore-mother-cells 

 in usual in the Leptosporangiate Ferns : in 

 [neimia Prantl figures 16 spore-mother-cells as seen 

 )m one side only of the sporogenous mass, and 

 have seen the same number in Mohria actually 

 traversed in a single section. These observations led to an enumeration 

 of the spores actually produced from the sporangia of the Schizaeaceae : 

 in Lygodium japonicum and dichotomum the number approximated to 256, 

 but in L. pinnatifidum to only 128: there is thus a difference between 

 species of the genus, as in Todea and elsewhere. The lower figure is 

 shared also by Schizaea? Mohria and Aneimia. The numbers are thus 

 larger than are seen in ordinary Leptosporangiate Ferns, and they approach 

 those seen in the Osmundaceae. The largest number is seen in Lygodium : 

 it will be seen that its anatomical characters also mark this genus out as 

 more archaic in structure than the rest of the family. 



FIG. 305. 



Diagram of segmentation of 

 a sporangium of the Schizae- 

 aceae ; the first segment wall 

 meets the periclinal (basal) 

 wall of the parent cell ; but 

 the second (_r, JT) meets the 

 first, and does not extend to 

 the base of the parent cell. 



ANATOMY. 



The Schizaeaceae show ' diversity of habit, varying from those with 

 creeping rhizome and laxly disposed leaves to those with ascending or 

 upright stock, and leaves densely spiral : the internal structure of the 

 shoot also shows marked differences, which follow these differences of 

 habit. 3 In Lygodium the simplest vascular structure is found, for there 

 the rhizome is traversed by a protostele with solid xylem consisting of 

 tracheides and parenchyma, surrounded by phloem, pericycle, and 

 endodermis. There is no typical proto-xylem : the first formed tracheides 



l L.c., p. 49. 2 Tansley and Chick, Ann. of Bot., 1903, p. 495. 



3 See Boodle, Ann. of Bot., 1901, p. 359, and 1903, p. 511; Jeffrey, Phil. Trans. , 

 B, 1902, p. 128; also Tansley and Chick, Ann. of Bot., 1903, p. 493. 



