460 COENOPTERIDEAE [CH. 



antennae. The crushed tissue lying on the outer face of each 

 of the loops probably represents the phloem and pericycle ; the 

 thin-walled elements above and below the horizontal band of 

 metaxylem are probably sieve-tubes. 



Fig. 316 shows a transverse section of a petiole of this 

 species : the loops, a, of small tracheae are seen bending round 

 the outer edge of the antennae. The inner and more delicate 

 cortical tissue is partially preserved and spaces, b, have been 

 formed in it as the result of contraction previous to petrifaction. 



Fig. 317. Ankyropteris corrugata. From a section in the Cambridge Botany 

 School Collection. ( x 9.) 



In the petiole represented in fig. 317 the tracheae of the 

 horizontal band are considerably crushed; the section is, how- 

 ever, of interest because of the presence of Lyginodendron 

 roots, I, in the space originally occupied by the inner cortex! 



In a paper on the tyloses of Jiachiopteris corrugata, Weiss^ 

 draws attention to the fact that similar inclusions have not 

 been found in the tracheae of recent ferns. The occurrence of 

 thin-walled parenchymatous cells in the large tracheae of 

 Ankyropteris corrugata petioles and of other species is a 

 striking feature. Williamson ^ compared these cells with the 

 tyloses in the vessels of recent flowering plants, and in a later 

 paper s he suggested that the included cells may belong to 

 saprophytic or parasitic fungi. It is, as Weiss points out, 

 1 Weiss, F. E. (06). 2 WiUiamson (77). s Williamson (88) A. 



