AMERICAN HONEY PLANTS 



197 



often fragrant; occasionally it is poisonous; often it is somewhat colored. 

 Commonly it is very fluid, but in the nectar-cups of poinsettia it becomes 

 very gummy. These properties come from substances— sugars, volatile 

 oils, poisonous organic compounds — that were made by and in the plant, 

 and they differ in different kinds of plants. Whatever bees or ants may do 

 in changing nectar into honey, they do not entirely change or remove 

 tl;ese substances, and the rank brown honey of the drug store is as easily 

 run to its source as the popular white clover honey, the daintily flavored 

 product of western, alfalfa, the aromatic acid honey of the red raspberry, 

 or the greenish product of the sweet clover with its delicate vanilla-like 

 aroma, the cumarin source of which shows itself in an occasional head- 

 ache, much as the minor organic constituents.of some honeys derived from 

 the heath family now and then prove seriously poisonous. 



A fluid that contains these organic substances necessarily falls into the 

 category of excretions or secretions, according as it represents waste or 

 usable material. As either excretion or secretion it is the product of spe- 

 cialized organs, glands, and its appearance marks these glands as in ac- 

 tion or performing their function. Whatever else may be- involved, this 

 depends upon the activity of their protoplasm, or is controlled by it. 

 When this is killed, secretion or excretion stops. 



All parts of plants are composed of individual cells flattened against one another. This figure 

 copied from Bonnier's "Les Nectaires," exhibits a longitudinal section of a stamen in 

 Coliiisia bicolor. Magnified. 



At left (34) cross section of filament. 



One result of the protean character of protoplasm is its different be- 

 havior in different plants, different organs of the same plant or different 

 phases of the activity of an individual cell. In either case it can perform 

 its functions only between certain limits of environment ,an(I it performs 

 them best somewhere between these limits. For each function and each 

 condition there is what physiologists call a minimum — 'below which it is 

 not carried on, a maximum — above which it has stopped, and an optimum — ■ 

 or most favorable. Just as in the efificient working of a human factory, 

 power and raw materials are necessary, and workmen must be onto the 

 job, however favorable the other conditions of manufacture may be. 



