250 APPENDIX 



Dandelion will answer, if young. Shepherd's Purse I have found 

 especially sensitive to light. Discuss geotropism and heliotropism 

 with class after these experiments. 



Exercise XXII. — Illustration i. Grass rhizomes wdll do. Iris is ex- 

 cellent, as it shows how the plant is propagated by lateral as well as ter- 

 minal buds. Useful examples of rhizomes will be found in any piece of 

 woods, under or in the leaf mold. Subterranean stems (Uvularia, 

 Smilacina, Polygonatum, Sanguinaria, etc.) are particularly interesting. 

 Keep in alcohol, rather than dry. For comparison with rhizomes intro- 

 duce such a caudex as Plantain. Also subterranean things like Trillium, 

 Jack-in-the-pulpit (beware of tasting). — Potato tuber. Artichoke 

 (from seedsmen or the market) may be substituted with advantage. 

 New potatoes from the garden have scales ; others may not have. — 

 Houseleek. May be ordered several months in advance from com- 

 mercial growers. As an alternative. Strawberry (pressed or alco- 

 holic) is suggested. — Asparagus. From florists: the large decorative 

 species known as Asparagus Sprengeri is the best. — Crocus. From 

 seedsmen, at about 1 cent each. Gladiolus and ]\Iontbretia are as 

 good but cost about 2 cents each. — Flowering Quince. The common 

 Thorn, or the Honey Locust (Gleditschia) may be used. — Boston 

 Ivy. Or the Grape ; in w^hich case the tendrils coil, without disks. 

 The Virginia Creeper (^Ampelopsis qidnquefolia) is figured in the text; 

 otherwise it would do for the present study. In all these cases the 

 tendril is, originally, the termination of the main stem, but is finally 

 turned aside by the growth of a lateral bud, which carries on the 

 growth of the vine. The effect is to make the tendril seem to spring 

 laterally, from opposite a leaf. The twisting of tendrils involves an 

 interesting question. (See the text.) Why the double twist, often 

 seen ? Hold both ends of a string fast then twist it by rolling at its 

 middle ; is the twist of entire string single or double ? 



Chapter IX. Exercise XXIII. — Experiment 1 1. Tropceolum is meant. 

 Several pupils may work together. Chlorophyll is extracted more 

 rapidly by alcohol in a test tube immersed in hot water. Then, to 

 swell starch grains, boil the bleached leaf in water. For carbon 

 assimilation, or photosynthesis, see Goodale, Ch. X., also the con- 

 cluding chapter in this book. For the liberation of oxygen as a 

 measure of assimilation, and directions for a most valuable experi- 

 ment (easy to perform if material is available), see Goodale, p. 30.5. 



In connection with the given experiments on assimilation in the 

 leaf, the observation of starch may be made if compound microscopes 

 are to be had. Use starch from potato, and perhaps from the pea 

 also. Starch being insoluble in water, the question arises how the 

 food which takes the form of starch can pass from one part of the 

 plant to another through the membranes of the plant body. (See 

 Digestion, § 560.) Observe digestion wi^h the compound microscope. 



