SEEDS AND SEEDLINGS. 211 



theme, and in learning the value of characters which aid us in 

 assigning plants to their proper categories. 



348. The three seedlings to be studied, For this reason 

 some of the illustrations of seedlings are introduced here, as 

 well as an account of their germination, and the means by which 

 they obtain food stored in the seed. In connection with this 

 reading the pupil can refer back to the plants studied in exer- 

 cises 1-4, and the teacher is at liberty to introduce here exer- 

 cises, if that seems desirable to further illustrate the subject 

 where there is an abundance of time. Three seedlings are 

 selected to illustrate the theme here ; the common garden bean, 

 the castor-oil bean, and the jack-in-the-pulpit. 



349. The common garden bean. The seed coats are nearly 

 filled with the two large cotyledons, which form the larger part 

 of the embryo. After the beans have been well soaked if one 

 is split lengthwise the young root and stem with the small 

 leaves will be seen lying between the cotyledons at one side. 

 There is no endosperm here now, since it was all used up in 

 the growth of the embryo, and a large part of its substance was 

 stored up in the cotyledons. As the seed germinates the young 

 plant gets its first food from that stored in the cotyledons. The 

 part of the stem between the cotyledons and the root (called 

 the hypocotyl in all seedlings) elongates, so that the cotyledons 

 are lifted from the soil. The hypocotyl is the part of the stem 

 here which becomes strongly curved, and the large cotyledons 

 are dragged out of the soil as shown in fig. 187. The outer 

 coat becomes loosened, and at last slips off completely. The 

 plumule (the young part of the stem with the leaves) is now 

 pushing out from between the cotyledons. As the cotyledons 

 are coming out of the ground the first pair of leaves rapidly 

 enlarge, so that before the stem has straightened up there is a 

 considerable leaf surface for the purpose of starch formation. 

 The leaves are at first clasped together, but as the stem becomes 

 erect they are gradually parted and come to stand out nearly in 

 a horizontal position. Fig. 187 shows the different positions. 



