SECTION 2.] 



A PATTERN PLANT. 



11 



Section TI. PLAX AS A PATTERN PLANT. 



8. Glrowth from the Seed. Phanerogamous plants grow from seed, 

 and their flowers are destined to the production of seeds. A seed has a 

 rudimentary plant ready formed in it, — sometimes with the two most 

 essential parts, i. e. stem and leaf, plainly discernible ; sometimes with no 

 obvious distinction of organs until germination begins. This incipient 

 plant is called an Embryo. 



9. In this section the Flax-plant is taken as a specimen, or type, and 

 the development and history of common plants in general is illustrated by 

 it. In flax-seed the embryo nearly fills the coats, but not quite. There 

 is a small deposit of nourishment between the seed-coat and the embryo : 

 this may for the present be left out of the account. This embryo consists 

 of a pair of leaves, pressed together face to face, and attached to an ex- 

 tremely short stem. (Fig. 2-4.) In this rudimentary condition the real 

 nature of the parts is not at once apparent ; but when the seed grows they 

 promptly reveal their character, — as the accompanying figures (Fig. 5-7) 

 show. 



10. Before the nature of these parts in the seed was altogether under- 

 stood, technical names were given to them, which are still in use. These 

 initial leaves were named Cotyledons. The initial stem on which they 

 stand was called the Radicle. That was because it gives rise to the first 

 root ; but, as it is really the beginning of the stem, and because it is the 

 stem that produces the root and not the root that produces the stem, it is 

 better to name it the Cadlicle. Recently it has been named Hypoeotyle; 

 which signifies something below the cotyledons, without pronouncing what 

 its nature is. 



Fio. 1. Pod of Flax. 2. Section lengthwise, showing two of the seeds; one whole, 

 the other cut half away, bringing contained embryo into view. 3. Similar section 

 of a flax-seed more magnified and divided flatwise; turned round, so that the 

 stem-end (cauliole) of the embryo is below: the whole broad upper part is the 

 inner face of one of the cotyledons; the minnte nick at its base is the plumule. 

 4, Similar section through a seed turned edgewise, showing the thickness of the 

 cotyledons, and the minute plumule between them, i. e. the minute bud on the 

 upper end of the cauliole. 



