44 



BIOLOGY OF PLANTS, 



2. Cotyledons are the seed lobes, as in the Fio- 5 

 garden bean, (Fig. 5,) and are composed of 

 matter to nourish the germ a 6, betbre it 

 can obtain food from the soil. Some seeds 

 have no cotyledons, such as those of the 

 mosses and ierns, and are called acotyle- 

 donous ; other seeds have but one cotyledon, 

 such as those of grasses, grains, etc. and 

 are called monocotyledonous ; otliers still 

 have two, as those of leguminous plants, (the pea,) and are 

 called bicotyledonous. A fourth class hav^e more than two cotyle- 

 dons, and are called polycolylcdonoiis^ of which the seeds of the 

 pine and hemlock are examples. 



3. Radicle. The radicle (Fig. 5, h) is that part of the embryo 

 which shoots downwards into the earth, and forms the roots of 

 plants. 



4. Plumula. The plumula, a^ is that part which shoots up- 

 ward into the air, and forms the stalk or stem, branches, leaves 

 and fruit. 



5. Bulhs are tubercles connected with the roots of Fig. 6. 

 plants, and contain the embryo of the future plant. 

 The potato (Fig. 6) is a well known example of a 

 bulb. 



6. Buds are vital points along the stem, situated 

 generally at the axles or angles of the leaves. The 

 bud (Fig. 7, « c) is caj)able of forming leaf buds, flowers, 



Fig. 7. 



