xxvj SPORANGIA 225 



cells become greatly enlarged, and their nuclei clustering round the sporo- 

 genous group of cells and undergoing fragmentation, present an appearance 

 very like that in Gleichenia. The central cell divides into 16 spore-mother- 

 cells, and the typical number of spores should be 64: but countings gave 

 figures between 48 and 64 as the produce of single sporangia. Sections of 

 sporangia so cut as to traverse the annulus throughout its course show the 

 wall as a single layer, but composed of more numerous cells than is commonly 

 the case in Leptosporangiate Ferns {D). The same is seen by examining 

 sporangia from without {A,B, C). Further, the short stalk is rather massive, 

 and consists of a peripheral series of six or seven cells surrounding a central 

 cell {A); this structure corresponds in its general features to that seen in 

 the massive sporangia of Gleichenia and Osmiinda. 



The mature sporangium is rather variable in form, owing probably to 

 pressures in the developing sorus. The annulus is incomplete and variable 

 in position, consisting of 20 or more cells which form a sinuous group, but 

 corresponding in the main with that in Gleichenia. The sporangia are often 

 tilted right or left, as in Fig. 501, B, which represents two sporangia in sitn 

 as seen from the side facing the indusium. Sporangia in which the annulus 

 is not tilted {A, C), show that it starts close to the stalk on one side, and 

 pursues a sinuous course round the head, but stops short at some distance 

 from the stalk at the side remote from the starting point. It is here that 

 the dehiscence takes place, but there is no specialised stomium. The spor- 

 angium at the centre of Fig. 501 is ruptured in this way. Thus the 

 sporangium of Ulatonia, while resembling that of Gleichenia in its general 

 features, differs from it in the variability of its structure, its lateral dehiscence, 

 and in the comparatively small output of its spores. While the general 

 comparison is thus with the Gleicheniaceae, the correspondence of the 

 details to those already described for Platyconia is remarkable (p. 209). 

 The abnormalities noted in that Fern serve to link the sporangial structure 

 of Matonia with the Gleicheniaceous type: for they illustrate the interrup- 

 tion of the annulus at the insertion of the stalk, and the assumption of the 

 lateral in place of the median dehiscence, though the stomium is ill-defined. 

 The spore-output per sporangium was found in Plaiy^oma to be 16 or 32, 

 in strong contrast to the much higher numbers in Gleichenia. But the out- 

 put in Matonia has not sunk so low as this, being typically 64. These facts 

 serve to connect the sporangial structure of the Matoniaceae with that of 

 the Gleicheniaceae. The plan of the sorus is the same in both, the chief 

 innovation appearing to be the presence of the indusium. But exuberant 

 growth of the receptacle at the vacant centre of the sorus readily accounts 

 for this biologically intelligible addition, while comparison may be made 

 with the somewhat similar vegetative growth from the apex of the sporangio- 

 phores of HeluiinthostacJiys (Fig. 364, G\ 



