VIII 



MARATTIALES 



285 



The proihalliiim does not die immediately after the young 

 sporophyte becomes independent, but may remain aHve for 

 several months afterwards, much as in Botrychiiim. 



The first tracheary tissue arises at the junction of the bun- 

 dles of the cotyledon, stem, and root. These primary tracheids 

 are short and their walls are marked with reticulate thickenings. 

 From this point the development of the tracheary tissue, as well 

 as the other elements of the bundles, proceeds toward the apices 

 of the young organs. The formation of the secondary 

 tracheids is always centripetal. 



Fig. 157. — A, Young sporophyte of Danaca simplicifolia, still attached to the gameto- 

 phyte, pr; X3; B, an older sporophyte of the same species; C, gametophyte of 

 Angiopteris evecta, with the young sporophyte. (A, B, after Brebner; C, after 

 Farmer.) 



Jefifrey (3) states that in the young sporophyte of several 

 species of Dancca examined by him, the stele has the form of a 

 tube with both internal and external endodermis and phloem. 

 Both internal endodermis and phloem tend to disappear in the 

 later-formed part of the stem. The tubular central cylinder is 

 interrupted by the foliar gaps, and later there are formed 

 medullary vascular strands, and the vascular system gradually 

 assumes the very complicated form met with in the older 

 sporophyte. Brebner (3) states that in Dancca simplicifolia the 



