204 STUDY OF COMMON PLANTS. 



II. Compare next the cultivated nasturtium, Tropceolum 

 majus, L., with the horseshoe geranium. 



1. Note the very different habits of the plant, the pecu- 



liarities of its foliage leaves, and means of pro- 

 tection. 



2. Observe the structure and plan of the flower. Note 



particularly the color of both calyx and corolla, 

 the guiding lines, nectar-tube, mode of guarding 

 the entrance to the latter, dichogamy, structure 

 of ovary, and number of carpels.^ 



III. In addition to the foregoing, study if possible one 

 or more indigenous species of Impatiens, or forms of the 

 cultivated " balsam " that have not become double. They 

 are of special interest as regards both the peculiar modi- 

 fications of the flower and the mechanism of seed dissemi- 

 nation. 



1. Comparing the plan of the flower with that of the 



species previously studied, try to ascertain whether 

 there has been consolidation or suppression of 

 parts, or both. 



2. Does the structure imply adaptation to cross-ferti- 



lization ? Does dichogamy exist ? 



3. If opportunity permits, observe what visitors Impati- 



ens has and their mode of operation. 



4. Examine ripe fruits and investigate the mechanism 



of seed dissemination. Is it the same in principle 

 as in Pelargonium and Geraniurri?^ 



Note. — The relationship of Pelargonium with the closely 

 allied genus Geranium is otvious, hut it differs in important 



1 Cf. Lubbock, I.e., pp. 75, 76. 



^ Cf. Duchartre, Elements de Botanique, p. 791. 



