614 FILICALES 
of the receptacle may grow up into a sporangium, developing as such in 
any order whatever, and without any regularity of orientation. The confused 
mass which results is shown in Fig. 339 c, and this also illustrates how, as 
the sporangia grow older, their stalks, composed in the lower part of but 
a single row of cells, become elongated. The vascular strand runs upward 
to a point immediately below the surface of the sorus, and there widens out 
amare 
pA 
Corr 
PRIX 
fil 
fl 
aa 
St 
Fic. 339. 
A=sorus of Dennstaedtia rubiginosa. Cut vertically and showing mixed condition in 
a sorus originally basipetal. B=Davallia Griffithiana, Hk. Young sorus in section, 
showing first formation of sporangia, C=old sorus of the same, showing sporangia of 
different ages intermixed. AII1x 100. 
into a considerable mass of tracheides, surrounded by a thin band of paren- 
chyma, and limited by a brown layer, which is doubtless of the nature of 
an endodermis. 
Examination of representatives of all the other sections of the genus 
Davaltia \ed to similar results, and it is thus seen that, with the exception 
of Microlepia, which had already been removed on other grounds by Prantl, 
and accorded a separate place by Christ,! the genus Daval/ia shows 
1 Farrnkriiuter, p. 10. 
