286 



THE OPHIOGLOSSALES 



forms at least. The spore mother cells are also distributed as 

 in Anthoceros, the essential difference being that they are sepa- 

 rated by a larger number of sterile cells and a larger number of 



-/^--\^'T' _ ~--~-..V"L . 



Fig. 216. Cross-section of a stem of Botrychium: p. pith ; x, xylem; 

 in, medullary ray; c, cambium; ph, phloem; c, endodermis ; cr, cortex.— 

 After Jeffrey. 



spore mother cells are also grouped together, forming rather con- 

 spicuous sacs or sporangia (Fig. 215, sp). The spores are formed 

 from the mother cells as in the Rryophyta and are discharged 



Fig. 217. Arrangement of the sporangia of an allied order, Marattiales: 

 A, leaflet of Archangioptcris with sporangia or surface of leaf and ar- 

 ranged in groups or sori. B, magnified view of a portion of the leaflet. 

 C, section of leaf, showing two sporangia, the left-hand one in section. 



from the sporangia through a transverse cleft (Fig. 215, E). It 

 is interesting to note in a closely allied order occurring in the 

 tropics, that the sporangia are developed directly upon the leaves 

 (Fig. 217) instead of upon special branches and that they are 

 sometimes associated together in groups, known as sori (sing. 



