DEVELOPMENT OF SPORANGIA. 



133 



Fig. 65. (After Luerssen.)— Development of the sporangia of Aspklmm Filix mas, 

 which is closely similar to that of Pterin, a, the young sporangium standing 

 upon the epidermis-cell from which it has just been divided; r, the proximal 

 cell cut off from the sporangium to form the pedicel and support the capsule; 

 a, 1, the first partition in the capsule; b, 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 oV^lique position of the partitions, and especially that of the 

 third ; /, a later stage ; 3, the origin of the tapetal cells and the formation of tlie 

 archesporium ; /«, division of the tapetal cells and the formation of the spore 

 mother-cells; I, four spores as they originate in the spore mother-cells; i, j, fc, 

 the annulus and ripe sporangium, in surface view ; j), peripheral cells; ar, 

 archesporium ; t, tapetal cells ; an, annulus. 



