214 STUDY OF COMMON PLANTS. 



Flower. 



I. Examine the flower in various stages of development. 

 Note 



1. The plan of the flower and how modified. 



2. The three-leaved involucel, " like an outer calyx." 



3. Insertion of the corolla and the relation of the latter 



to the stamen-tube (best seen on longitudinal sec- 

 tion). 



4. The monadelphous stamens, 



5. Form and mode of dehiscence of anthers. 



6. Number of stigmas. Does this correspond with the 



number of divisions of the ovary ? 



II. Ascertain whether there are any adaptations favor- 

 ing cross-fertilization, or any that render self-fertilization 

 impossible. 



1. Are there any guiding lines ? 



2. Is nectar produced? If so, is it protected in any 



way? 



3. Compare flowers of different ages and ascertain 



whether dichogamy exists.^ 



Fruit and. Seed. 



I. Examine the fruit, making both transverse and longi- 

 tudinal sections of specimens of different ages. Ascertain 



1. The number of carpels. 



2. Form and place of attachment of the ovules. 



3. Structure and position of the embryo. (This is 



easily made out with a lens by means of repeated 

 sections, trying different specimens until the most 

 favorable ones are found.) 



^ Lubbock, British Wild Flowers in Belation to Insects, p. 41 ; Ifiiller, 

 Fertilization of Flowers, pp. 142, 143. 



