216 MORPHOLOGY. 



found in the embryonic life, and only little scale-like ones at a very late 

 period after germination. 



The different modifications of the form of the embryo and its parts 

 will be treated of subsequently when speaking of the seed. Here it was 

 only dealt with in order to become acquainted with so much of the 

 course of development as appeared necessary to the comprehension and 

 the establishment of what follows. Indeed, it is always dangerous to 

 interfere in the current of organic development and to define the com- 

 mencement. Are we to begin with the egg because the hen originates 

 from it, or with the hen because she lays the egg ? Great circumspection 

 is necessary to arrive at the simplest point of departure, and repetitions 

 are unavoidable, since, in order to completeness, we must make the 

 circle of development return again into itself. 



122. After a variable period of rest, the development of the em- 

 bryo into a plant (germination) commences, upon which it throws 

 off the coats of the seed enclosing it. The same process which ef- 

 fected the perfect formation of the embryo now recommences ; 

 the radicle elongates into the root and forms branches, and the axis 

 elongates in its appointed manner, and at the same time conti- 

 nuously pushes forth leaves. Thus originates the simple Phanero- 

 gamous plant. The axis and leaves, however, gradually assume, 

 through different forms and conditions of position, a different mor- 

 phological import, until their power of development is exhausted 

 by the formation of a new individual, and ceases. From the axis 

 are frequently developed, in a way very different from the forma- 

 tion of the radicle and its ramifications, organs which, on account 

 of their many essential agreements with true roots, we call adven- 

 titious roots (radices adventitice). But the plant seldom or never re- 

 mains simple ; in the angles which the leaves make with the upper 

 internodes, the axils of the leaves, fresh processes of cell-formation 

 originate which form rudimentary axes and leaves, repeating the 

 formation of the embryo, but without radical extremities, and these 

 are collectively called axillary buds. Under certain circumstances, 

 also, new individuals of this kind originate on the axis, scattered 

 buds ; finally every axis, whether it be that of a simple plant, or 

 one which has issued from a bud, naturally terminates in the rudi- 

 ment of an axis, and a number of more or less rudimentary leaves, 

 which are collectively named the terminal bud. Thus we obtain 

 the following survey of the portions of the plant, which must be 

 individually more closely examined : 



A. Radical organs. 



1. The radicle and its development. 2. The adventitious roots. 



13. Axial organs. 



1. The axis and its development. 2. The receptacle, the disc. 

 3. The placenta. 4. The seed bud. 5. The seed. 



C. Foliar organs. 



1. The leaf. 2. The floral envelopes. 3. The stamen. 4. The 

 carpel. 5. The fruit. 



