DEVELOPMENT OF PLANTS 



301 



tures that recall the sporophyte of AntJioceros (Figs. 215, B; 

 199). The outer portion of the cylinder consists of chlorophyll- 

 bearing cells which communicate with stomata in some of the 





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

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

 After Jeffrey. 



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 largei number of 



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

 A, leaflet of Archangiopteris with sporangia on surface of leaf and arranged 

 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. 



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 Bryophyta and are discharged 

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



