EXPERIMENTS AND PRACTICAL WORK 



37 



taken by the yam. Note whether the yampie is also a 

 twiner or not, and, if it is, in what direction it grows. 



Expt. 28. Shapes and Coverings 

 of Stems. Collect : 



(a) Six round (cylindrical) stems, 

 e.g. soursop, genip. 



(b) Four three-sided (triangular) 

 stems, e.g. bine -pear, Jerusalem 

 candlestick. 



(c) Four four-sided (quadrangular) 

 stems, e.g. granadilla. 



(d) Six stems with smooth sur- 

 faces, e.g. mango, sweet potato. 



(e) Four stems with hairs, e.g. 

 cowitch. 



( /) Four stems with hollow joints, 

 e.g. bamboo, wild cane. 



Expt. 29. Protective Hairs and 

 Prickles. What purpose does it 

 seem likely that the hairs on the 

 cowitch (which should not be 

 handled) and the prickles of the 

 prickly pear serve? Make drawings of hairs and 

 prickles. 



Expt. 30. Layers of Bark, Wood, and Pith. Examine 

 young plants of broomweed, and note that the pith gets 

 smaller while the woody part enlarges. 



Expt. 31. Heartwood and Sapwood. Examine logs 

 of wood cut from branches of large trees, and observe 

 that there are two layers of wood the hard and darker- 

 coloured heartwood in the centre and the outer layer 

 of sapwood. 



Expt. 32. Stems of Monocotyledons and Dicotyledons. 

 Get portions of the stem of the corn, mango, cane, 

 and sunflower plants; saw across, and make drawings 



Fig. 16. Twining Stem 



