402 A TEXT-BOOK OF BOTANY. 



the transferral of tlie pollen in cross-pollination are called ento- 

 MOPHiLOUS (Fig. 229). They frequently possess bright, highly 

 colored flowers, and it is considered that these serve as an attrac- 

 tion to the insects which visit them. The insects are, however, 

 probably more attracted by the odor and food products which 

 they obtain, such as the nectar. The nectar is secreted by glands 

 known as nectaries, which are variously located ; frequently 

 they are on the torus, either between the ovary and stamens 

 (Fig. 78) or between the stamens and petals. Sometimes the 

 stamen is modified to a nectar-secreting spur, as in the violets. 

 In aconite the nectary is developed from one of the posterior 

 petals (Fig. 223, E). In seeking the nectar the pollen of the ripe 

 anther may fall upon or adhere to the insects and thus be carried 

 from one flower to another (Fig. 230). 



Honey is a product formed through transformation of the 

 plant nectar by honey bees. The nectar is supposed to be acted 

 upon by certain salivary secretions of the bee and changed into a 

 fruit-sugar, the so-called honey, consisting of a mixture of dex- 

 trose and levulose. The nectar of buckwheat and clover (partic- 

 ularly white clover) is the principal source of the commercial 

 article. The nectar of some plants is poisonous and may furnish a 

 poisonous honey (see discussion under Ericaceae). 



THE INNER STRUCTURE OF THE FLOWER. 



The inner structure of the flower bears a close resemblance 

 to that of the stem and leaf. The bracts in almost all particulars 

 are like the foliage leaf of the same plant, and the flower stalk 

 closely resembles the foliage stem. The calyx, while resembling 

 the foliage leaf, usually contains calcium oxalate in greater amount, 

 and the chlorenchyma consists wholly of rather loose chlorophyll 

 parenchyma ; the outer or under epidermis contains the stomata, 

 and if hairs are present, they also arise from this surface ; the 

 fibrovascular bundles are generally simple in structure, although 

 in some cases, as in lavender, sclerenchymatous fibers are strongly 

 developed. 



In the COROLLA the epidermal cells are generally more or less 

 centrifugally developed, forming prominent papillae (Fig. 232, 

 A, B), which give the petals a velvety or satiny appearance, as in 



