io8 



SEEDS AND SEEDLIiNGS 



A good germinator can be made by putting moist sand or sawdust 

 between two plates. The germinator sliould be kept at an even tem- 

 perature of about 20° C. (70° F.). Seeds even of the same Icind develop 

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

 more than two plantings of each sort, about 4 or 5 days apart. Enough 

 must be provided to give each pupil 3 or 4 specimens in different 

 stages of development. 



145. Seedlings of Monocotyledons. — Examine a grain of 

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



J40 the seedling 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. Examine each 

 carefully with regard to the cotyledon, 

 the root, and the plumule. Which part 

 first appeared above the ground .'' In 

 what direction does the plumule grow.' 

 The hypocotyl.'' Does the cotyledon 

 appear above ground at all.' Slip off 

 the seed coats and see if there is any 

 difference in the size and appearance 

 of the contents as you proceed from 



the younger to the older plants. How would you account 



for the difference .'' 



146. The Cotyledon. — Is the cotyledon of any use to the 

 seedling when it remains in the ground.' In order to 

 answer this question, cut away carefully, so as not to injure 

 the plumule, the cotyledon with its endosperm, from a 

 very young seedling, and place on a piece of coarse netting 

 stretched over a glass of water so that its roots will touch 

 the liquid. Put beside it another seedUng of the same age 

 and size from which the cotyledon has not been removed, 

 and watch their growth for a week or ten days. Which 

 has developed most rapidly in that time .' Test the coty- 



240, 241. — Seedling 

 of corn {after GRAY) : 

 240, early stage of 

 germination ; 241, later 

 stage. 



