8 PART I. ORGANOGRAPHY. 



Fig. 4, tuberous ; roots which are wholly slender and thread-like, 

 as those of most grasses, Fig. 8, fibrous ; and roots which terminate 

 abruptly, as if bitten off, premose. 



Practical Exercises. 



Cause some seeds of common plants, as the Pumpkin, Pea, Corn, etc., to 

 germinate over water so that the roots do not pass into the soil. A convenient 

 way is to fill a wide-mouthed bottle half or two-thirds full of water, and, after 

 fitting a cork to it, fasten by means of wires the seeds to the under surface of 

 the cork, and insert it in the mouth of the bottle, and set the latter away for a 

 few days in a warm place. The seeds will soon germinate, and the forms of 

 their roots, and their structure and habits of growth, may be studied. 



Observe and describe the forms and modes of branching of the different 

 roots ; by means of the magnifying lens study the root-hairs, observing on what 

 parts of the rootlets they are most abundant ; determine whether the roots are 

 primary or secondary in their character, and examine the tips of the roots for 

 the root-cap. Procure specimens of the common Duck-weed, in which the 

 root-cap is highly developed, and examine it with care. As examples of aerial 

 roots, study those of the Ivy, and as examples of the roots of parasites, study 

 those of the common Dodder or of the Mistletoe, making sections of them and 

 of their host-plants in such a way as to observe how the roots penetrate the 

 bark of the host. 



Record, in appropriate descriptive language, and by means of drawings, 

 the results of your observations. 



CHAPTER II.— THE STEM. 



The stem may be described as that part of the plant-axis 

 which bears leaves or some vwdification of them. Its ordinary 

 functions are to form such a support for the leaves as will duly 

 expose them to the influence of the light and air, to bear the 

 floral organs and convey to them the nutriment they require, and 

 to form a means of communication and interchange between the 

 roots, or organs which absorb the crude nutritive materials from 

 the soil, and the leaves, or organs which assimilate these 

 materials. But, like other vegetative organs, they are often 

 modified, as we shall presently see, so as to subserve functions 

 quite different from the normal. Besides bearing roots, leaves 

 and hairs — appendages different from itself — a stem, commonly, 

 though not always, bears branches, or appendages essentially 

 like itself. A stem differs from a root not only in the fact that 



