46 



VASCULAR CRYPTOGAMS 



reduced to only one. Each fertile leaf or sporophyll subtends only a 

 single sporange, which is borne on the stem above the leaf-axil. The 

 sporanges are of considerable size in proportion to that of the leaf, and 

 are formed from a group of superficial cells at the growing point of the 

 stem. They make their first appearance as flat, afterwards spherical or 



club-shaped, swellings, completely 



covered by the epiderm, which 



A ^ ' il'W \ 1 subsequently forms, by tangential 



divisions, the wall of the sporange, 

 composed of three layers. By 

 subsequent growth the sporange 



Fig. 27.— Section of megasporange of ^. 

 incpquali/olia, showing double wall of 

 sporange, layer of tapetal cells, and mega- 

 spores. (After Goebel, magnified.) 



comes to be placed in the axil or 

 even on the base of the leaf. The 

 ' vascular ' bundle of the leaf passes 

 beneath the sporange without 

 sending a branch into it. As in 

 the other heterosporous families, 

 the two kinds of sporange present no differentiation in their early 

 stages. The archespore is the terminal hypodermal cell of an axial row. 

 This divides into the sporogenous tissue surrounded by the layer of tapetal 

 cells formed from the innermost of the layers of cells into which the wall 

 of the sporange divides. In the megasporanges one of the spore-mother- 

 cells grows more vigorously than the rest, which gradually abort. In this 



Fig. 26. — A^ fertile branch of 6". itK^qjiali- 

 folia (half natural size). B, longitudinal 

 section of upper part showing microspo- 

 ranges and megasporanges. (After Goebel, 

 magnified.) 



