INTRODUCTORY 



begins to grow a " big root." In a -Jnllrnr- nitr, lilir nrrn may grow as 

 represented in Fig. 14. Orange seeds may have puzzled you, but now 



14. Germinating seed of Big-root (Mejarrhiza) three fourths natural sizo. 



two or three plumules and as many radicles growing from one 

 seed prove that it has more than one embryo. You readily 

 distinguish the grass-like plumules of the monocotyledonous 

 seeds from the broader leaved plumules of the dicotyledons. The rad- 

 icles, too, send out roots in a differ- 

 ent way. (Figures 15 to 17.) 



11. By this time you cannot fail 

 to see that the embryo is a little plant 

 in the seed. The radicle answers to 

 the stem and roots ; the cotyledons 

 are leaves, and the plumule is a bud 

 from which is to grow the entire 

 above-ground portion of the plant. 

 Study the relations between the facts 

 you observe until you can, at least, 



answer the following 



'* * r f /^* 



17 



15. Germinating corn. 10- Whea. 17- 

 Wild onts: a colorless sheath iuclnsinf* the fir-t 

 plumule l"af l>; <, the twisted and bent beard 

 which enables it to plant itself. 



QUESTIONS. 1. How many coats have 

 most of the seeds which you have examined? 

 2. What part or parts of the embryo be- 

 come green ? 3. What causes the green- 

 nes'3 of plants ? 4. What kind of cotyledons remain underground in germination ? 



5. What can you say of the plumule of embryos whose cotyledon:; become leaf-like? 



6. Do the cotyledons of albuminous dicotyledons appear above ground? 7. Why 

 should the plumule of a bean be larger than that of a squash ? 8. What becomes of 

 the albumen in a seed ? 9. What nourishes the growing radicle and plumule of an 

 acorn or a pea? 10. Can you give reasons for calling the cotyledons seed-leaves 



