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 



FIG. 339. 



A =sorus of Denn staedtia rnbiginosa. Cut vertically and showing mixed condition in 

 a sorus originally basipetal. B = Davallia. Griffith.ia.na, Hk. Young sorus in section, 

 showing first formation of sporangia. C = old sorus of the same, showing sporangia of 

 different ages intermixed. All X 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 

 Davallia led 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, 1 the genus Davallia shows 



1 Farrnkrauter, p. 10. 



