PRACTICAL WORK. NO. X. 217 



e. the pericycle ; 



f. sieve-tubes with lateral sieve-plates ; 



g. scalariform vessels of the xylem. Your section may 

 possibly also shew spiral vessels of the protoxylem, though 

 they will be more easily seen in the macerated material. 



v. Spread out gently in a drop of water a small piece 

 of Pteris rhizome that has been macerated, and identify 

 the various tissue elements already sketched from your 

 sections, observing especially sclerenchymatous cells, sieve- 

 tubes with irregular reticulate thickening, and the spiral 

 and scalariform vessels of the xylem. 



No. X. 



THE REPRODUCTION OF THE FERN. 



i. Cut a section of the leaf of Pteris preserved in 

 alcohol and mount it in glycerine. Sketch your section 

 under the low power, shewing the numerous stalked 

 sporangia arising from the placenta, the whole sorus being 

 covered by the recurved margin of the leaf. 



ii. Cut a section of the leaf of Aspidium, passing 

 through the centre of one of the numerous white kidney- 

 shaped bodies, each of which is a sorus covered by its 

 indusium. Shew on your sketch stalked sporangia borne 

 on a placenta and covered by the umbrella-shaped in- 

 dusium. 



iii. Place a few sporangia from the wetted sorus of 

 Poly podium aureum on a slide, in the smallest possible 



