GERMINATION AND GROWTH 



41 



develop at such different rates that it will probably not be necessary to 

 make more than two plantings of each sort, from 2 to 5 days apart. 

 Soaked seeds of corn and wheat will germinate in from 3 to 7 days, 

 according to the temperature; oats in 1 to 4; beans in 4 to 6; 

 squash and castor beans in from 8 to 10. Very obdurate ones may 

 be hastened by clipping. Keep the germinators in an even temperature, 

 at about 70° to 80° F. 



Pine is a very difficult seed to germinate, requiring usually from 18 to 21 

 days. By soaking the mast for twenty-four hours and planting in damp 

 sand or sawdust kept at an even temperature of 23° C. or about 75° F., 

 specimens may be obtained. 



L 



36. Seedlings of monocotyls. — Examine a seedling of 

 corn that has just begun to sprout ; from which side does the 

 seedhng spring, the plain or the grooved one ? Refer to your 

 sketch of the dry grain and see if this 



agrees with the position of the embryo as 

 observed in the seed. Make sketches of 

 four or five seedlings in different stages of 

 advancement, until you reach one with a 

 well-developed blade. From what part of 

 the embryo has each part of the seedling 

 developed? Which part first appeared 

 above ground? Is it straight, or bent in 

 any way? In what direction does the 

 plumule grow ? The hypocotyl ? Does the 

 cotyledon appear above ground at all? Slip 

 off the husk and see if there is any differ- 

 ence in the size and appearance of the 

 contents as you proceed from the younger 

 to the older plants. How would you ac- 

 count for the difference? 



37. The root. — Examine the lower end of the hypocotyl 

 and find where the roots originate ; would you say that they 

 are an outgrowth from the stem, or the stem from the root ? 

 Observe that the root of the corn does not continue to grow 

 in a single main axis like that of the castor bean, but that 

 numerous adventitious and secondary roots spring from 



Figs. 54, 55.— Seed- 

 ling of corn {after 

 Gray) : 54, early stage 

 of germination ; 55, 

 later stage. 



