INDUSIUM AND SPORANGIUM. 



91 



FIG. 53. (After Luerssen.) Development of the sporangia of Aspidium Filix mas, wm'ch 

 is closely similar to that of Pteris. a, the young sporangium standing uoon the epider- 

 mis-cell from which it has just been divided; .r, the proximal cell cut off from the spo- 

 rangium to form the pedicel and support the capsule, a, 1, the first partition in the cap- 

 sule; &, 1 and 2, the first and second partitions; c, 1, 2, 4, the first, second, and fourth 

 partitions; d and e are cross-sections of the capsule showing the oblique position of the 

 partitions, and especially that of the third; /, a later stage; g, the origin of the 

 tapetal cells and the formation of the archesporium ; h, division of the tapetal cells and 

 the formation of the spore mother-cells; ?, four spores as they originate in the spore 

 mother-cells; i, j, fc, the annulus and ripe sporangium, in surface view, p, peripheral 

 cells; ar, archesporium; t, tapetal cells; an, annulus. 



