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A TEXTBOOK OF THEORETICAL BOTANY 



which is so common in all Fern stems and roots, is due to phenolic con- 

 densation products called phlobaphenes, chemically related to Bakelite, the 

 well-known plastic material. A rare anatomical peculiarity found in 

 the Male Fern is the occurrence in the cortex of many schizogenetic cavities 

 lined with glandular hairs. These internal hairs secrete a resin which is a 

 valuable vermifuge. 



The stems of all Ferns grow from a single apical cell, which is usually 

 shaped like a three-sided pyramid, with its base uppermost. This cell divides 

 repeatedly, parallel to each of its three sides, and from it are derived all the 

 cells of the mature tissues. In this the Ferns differ from the Spermatophyta, 

 where, as we have previously seen, there is an apical meristem tissue, not a 

 single apical cell. 



Anatomy of the Leaf 



The leaves of the full-grown Male Fern are large, and consequently we 

 find that five to seven leaf traces pass out from the stele into the petiole. 



Fig. 474. — Dryopten's fi/ix-?}ias. Transverse section 

 through the petiole showing horseshoe arrange- 

 ment of meristeles. From the two large adaxial 

 meristeles the pinna traces are given off. 



In transverse section the petiole is roughly semicircular in outline, the 

 flattened side being adaxial, that is, towards the stem. The meristeles are 

 arranged in the shape of a horseshoe with the points towards the adaxial 

 side of the petiole, and are embedded in ground parenchyma, which is 

 surrounded on the periphery' by several layers of sclerenchyma (Fig. 474). 

 In the upper part of the rachis the two marginal steles of the horseshoe 

 give off branches to each pinna, and from these in turn branches are given 



