256 



LOXSOMACEAE 



[CH. 



genera is short, being composed of about six rows of cells. The dehiscence 

 o{ Loxsoina being distinctly anomalous, while that oi Loxsomopsis is closely 

 comparable with that of Dicksonia and other Gradate Ferns, it seems right 

 to seek an interpretation of the sporangia of the older genus in terms of the 

 normal type. A simple explanation seems to be that Loxsonia originally had 

 a sporangium like that of Loxsoviopsis, with a lateral stomium: but that as 

 the cup-like indusium fitted close round the receptacle in relation to its 

 protective function, the lateral dehiscence became mechanically ineffective. 

 The lovv^erhoop of the annulus, including the stomium, then became vestigial, 

 as we actually see it to be (Fig. 521, C, D). Rupture was, however, provided by 

 a new slit in the middle of the indurated distal curve of the ring, a position 



/; c 



4M 



Fig. 524. Sporangia of Loxsomopsis notahilis, from three difterent aspects. C shows the sporangium 

 in natural position on the receptacle (shaded), with attendant hairs, as in Loxsovta. The distal 

 face is to the left. A has its distal face upwards, and shows the stalk as in Loxsovta, but the stomium 

 is lateral and well formed. B has the distal face to the right and dehiscent stomium to the left. 

 Note that the dehiscence B and C is to the left of the sporangium, and that in A to the right. 

 Thus it is not constant. ( x '250.) 



that proved more convenient. If this were so then the median dehiscence 

 of Loxsonia is not a survival of that of the .Simplices, but a new feature. 

 Certainly the slit occurs at the point most convenient for the shedding of 

 the spores (compare Vol. I, Fig. 206). If this view be correct, one of the most 

 interesting points in Loxsonia for comparison with the Simplices falls away, 

 and the Loxsomaceae appear as ordinary Gradate Ferns with basipetal 

 sequence, and originally lateral dehiscence, right or left, as in Loxsouwpsis. 

 But in Loxsonia a mechanical difficulty has been met by adopting secondarily 

 a distal rupture. 



The number of spores in Loxsonia is 64, and they are of a large size. 



The Gametophyte 

 In a family so interesting as the Loxsomaceae it is important to 

 know the characters of the gametophyte, and von Goebel has supplied an 



