12 STUDIES OF SEEDS AND SEEDLINGS 



Exercise YI. The Development of the Seedling 



Experiment 6. — An exceedingly important change undergone by 

 tlie seedling as it comes out of the soil or the seed into the light, 

 may easily be overlooked. In order to single out this effect from 

 others observed in the course of the young plant's development, next 

 to be studied, germinate some seeds in the dark, and let the seedlings 

 develop quite away from the influence of light. Their increase of size 

 and the succession of parts will be much like that of ordinary seedlings, 

 and their appearance similar except in the one vital particular — a 

 characteristic of plants so commonplace that it is hard to realize its 

 true importance. 



In the course of the studies below let the above seedlings, and per- 

 haps others grown in very dim light, be compared with those grown 

 in full light. 



Turning now to the general developmenl: of the seedling, the 

 student should consider afresh that every buried seed contains a 

 nascent plant, and that at the start it is confronted by a complicated 

 problem. In many cases the very first difficulty is how to escape from 

 the wrappings of the seed itself. After that there is the question how, 

 through growth from a very limited food supply, on the one hand to 

 reach the air and spread a small crown of leaves, and on the other to 

 establish connection with the soil. 



Germinate seeds of Squash, Onion, White Lupine, Pea, and Morn- 

 ing Glory, to various stages. Write notes along the lines indicated 

 below, and illustrate by drawings. 



1. Any special methods of getting free from seed coats. 



2. Whether the cotyledons are raised out of the ground or not. 



3. The mode of extracting cotyledons or plumule from the soil. 



4. Whether the cotyledons serve as food sacs, as foliage leaves, or 

 as both. 



5. In which cases the plumule develops early, in which late ; 

 reasons. 



6. In albuminous seeds, what organ of the embryo acts to absorb 

 the albumen. 



On points calling for individual judgment rather than statement of 

 facts, let the opinion formed by the pupil be expressed distinctly as 

 such. 



Supplementary Topics for Investigation 



1. The rudimentary embryos of orchids. Material, seeds of native 

 or greenhouse plants. Polj^embryony of Spiranthes cernua. 



2. Embrj^os of certain Conifers. Pinus Lambertiana, P.pinea, or 

 even smaller seeded species for the seeds. Larix Americana (Hack- 

 matack) and Picea excelsa (Norway Spruce) for germination. 



