PROPAGATION BY SEEDS 51 



69. Time of germination. The time required for germi- 

 nation varies with the kind of seed from a few days to a month 

 or more, a fact which must be taken into account in the plant- 

 ing. Nursery catalogues and books on gardening frequently 

 give the time required for germination of various seeds. 



70. Transplanting. Young plants are sometimes started 

 in the greenhouse, and later planted out-of-doors. They may 

 be transplanted from flats or hotbeds into coldframes before 

 they are set out in the field. Coldframes are similar to hot- 

 beds except that no heating material is used. The sun shines 

 through the glass frame during the day, warming the bed, 

 and at night the covering keeps the heat from radiating too 

 rapidly and prevents frost from injuring the plants. Some- 

 times young plants are placed in pots and set out-of-doors 

 before being planted in the open, or repotted into larger pots 

 from small ones. 



EXERCISES 



EXERCISE I. Structure of seeds. 



Materials. Seeds of corn, pumpkin, bean, pea, and other plants; 

 knife; dissecting pin; magnifying glass. 



Procedure. Prepare seeds in the manner suggested in paragraph 49. 

 Locate in each the hilum, micropyle, cotyledons, plumule, and caulicle. 

 Classify the seeds examined into monocotyledonous and dicotyledonous 

 seeds. Prepare a table showing wherein the seeds examined are alike 

 in structure and wherein they differ. Make outline drawings of a few 

 types of the seeds examined, labeling the parts. 



EXERCISE II. Growth of the plant parts. 



Materials. Seeds similar to those studied in the preceding exercise; 

 small boxes; sawdust or clean sand. 



Procedure. Plant seeds in boxes filled with sand or sawdust kept 

 moist, and dig up some every few days to determine the manner of 

 growth of the parts. Observe what parts of the plant the plumule 

 and caulicle become. What becomes of the cotyledons in each case? 

 Write your observations as to how plants grow and illustrate with out- 

 line drawings. 



