4 BOTANY. 



6. Parts of the pumpkin seedling. — During the germination 

 of the seed all parts of the embryo have enlarged. This in- 

 crease in size of a plant is one of the peculiarities of growth. 

 The cotyledons have elongated and expanded somewhat, though 

 not to such a great extent as the root and the stem. The 

 cotyledons also have become green on exposure to the light. 

 Very soon after the main root has emerged from the seed coats, 

 other lateral roots begin to form, so that the 

 root soon becomes very much branched. 

 The main root with its branches makes 

 up the root system of the seedling. Be- 

 tween the expanded cotyledons is seen 

 the plumule. This has enlarged some- 

 what, but not nearly so much as the root, 

 or the part of the stem which extends 

 below the cotyledons. This part of the 

 stem, i. e. , that 

 part below the 

 cotyledons and 

 extending to the 

 beginning of the 

 root, is called in 

 all seedlings the 

 hypocoiyl, which means ' ' below the cotyledon. ' ' 



Fig. 3. 

 Pumpkin seedling rising from the ground. 



Exercise 1 . 



7. Structure of a squash or pumpkin seed. — Sketch a squash or pumpkin 

 seed, noting carefully the form and markings. Split off the tough papery 

 seed coats (testa), from a seed which has been soaked in water, to observe 

 the embryo. Note the large, flattened cotyledons. Spread them gently apart 

 to see the attachment at the smaller ends, where they are attached to the 

 short caulicle (stem). Sketch the embryo in this position showing the 

 cotyledons, the plumule between them, and the short radicle projecting from 

 the end where the cotyledons are attached; name the parts of the embryo. 

 Make a cross-section of another seed through the middle, and observe the 

 relation of the cotyledons to the seed coats; sketch. Make a cross-section 



