322 PRACTICAL BOTANY 



strengthen the superficial tissues ; (c) two internal 

 layers, the inner of which has thickened brown 

 walls. 



3. The endodermis, consisting of narrow cells. 



4. The central vascular cylinder, similar in general 

 arrangement to that of other Ferns, but of a reduced 

 type : usually only eight elements of xylem, very regu- 

 larly arranged to form a diarch plate, are to be seen 

 in the transverse section: the phloem is very much 

 reduced. 



Preparations should also be made of the apex of the stem, and 

 of the root as above directed for other Ferns. 



V. Cut transverse sections of the mature sporocarp, 

 these are to be found in large numbers on the plant in 

 August and September : mount in pure glycerine, and 

 examine under a low power. 



The circular section will be found limited by a thick 

 and firm wall, bearing external hairs : the internal 

 space is partitioned into four loculi by septa of thin- 

 walled tissue. Projecting from the outer wall into 

 each loculus is a cushion-like placenta, upon which 

 are inserted the numerous sporangia: these are of 

 two sorts, macrosporangia, which contain each a 

 single large macrospore, and microsporangia, each 

 containing numerous smaller microspores. 



Examine the section under a high power, and observe 

 that the wall of the sporocarp consists of 



a. A very irregular layer of epidermis, with stomata, 

 having two depressed guard-cells : note also the inser- 

 tion of the superficial hairs. 



I, Two layers of very regular prismatic cells, closely 



