102 



GERMIXATIOX OF SEEDS: SEEDLINGS 



of a plant's life-C3'clc into successive stages is somewhat artificial, 

 for the stages so overlap that they can not be separated. In tJiis 

 presentation we are chiefly concerned with the seedling stage — • 



the stage in which plants 

 present differences that 

 sometimes must be reck- 

 oned with in choosing 

 proper methods of plant- 

 ing and cultivating, and 

 that often explain the 

 peculiar features of the 

 plant in the adult stage. 

 Among our cultivated 

 plants there are four rather 

 distinct types of seedlings 

 as those of the Grasses, 

 Onion, Beans, and Peas 

 illustrate. 



Seedlings of the Grass 

 Type. — The seedhngs of 

 all Grasses are so similar 

 in type that their essential 

 features may be learned 

 by studying the seedling 

 stage of Corn. From Fig- 

 ure . 95, showing the de- 

 velopment of the Corn 

 seedling, it is seen that the 

 radicle develops directly 

 downward, forming the 

 first root called 'primary 

 root from which secondary 

 roots arise as branches. 

 However, not all second- 

 ary roots arise at this time 

 from the radicle, for some 

 often grow out from the stem just above or below the cotyledon. 

 The plumule, although developing more slowly at first than the 

 radicle, soon breaks through its sheath-like covering (coleoptile) 

 and rapidly elevates its leaves to the light. As the plumule is 



Fig. 96. — A later stage of the Corn seed- 

 ling, g, ground line; p, plumule; a, first 

 node with permanent root system; b, portion 

 of stem between the first node and kernel; 

 k, kernel; r, radicle or primary root; s, sec- 

 ondary roots of the primary root system; 

 d, permanent root system; c, coleoptile. 

 About half natural size. 



