310 



FILICALES 



[ClI. 



consisting of thin-walled parenchyma and, in most ferns, a 

 considerable quantity of hard and lignified mechanical tissue. 

 The narrow protoxylem elements are usually characterised by a 

 spiral form of thickening, but in slow-growing stems the first- 

 formed elements are frequently of the scalariform type. 



A study of the anatomy of recent ferns both in the adult 

 state and in successive stages of development from the embryo 

 has on the whole revealed "a striking parallelism'" between 

 vascular and sporangial characters in leptosporangiate ferns. 

 For a masterly treatment of our knowledge of fern anatomy 



Fig. 237. 



A. 

 B. 

 C. 



D. 



E. 



Matonia pectinata (petiole). 



M. pectinata (stem). 



Gleichenia dicarpa (stem) : p, petiole ; pp, protophloem ; 



position of protoxylem indicated by black dots. 

 Matonidium. 

 Trichomanes reniforme : pp, protophloem. 



(C, E, after Boodle; D, after Bommer.) 



from a phylogenetic point of view reference should be made to 

 Mr Tansley's recently published lectures : within the limits of 

 this volume all that is possible is a brief outline of the main 

 types of vascular structure illustrated by recent genera. 

 To Prof Jeffrey 2 we owe the term protostele which he applied 



1 Tansley (08) p. 27. 2 Jeffrey (98). 



