18 



SEEDS AND SEEDLINGS 



6. Embrj oof the Yel- 

 low Pond Lily 

 (magnified). 



the cotyledons, with several of the first leaves which it 

 will bear (Fig. 6). This bud of the ascending axis, already 

 developed in the seed, is the plumule. 

 In the Bean and similar strong embryos 

 the leaves of the plumule are already 

 perfect as concerns outline, veining, 

 and so on, and need only to gain green 

 color and a larger size to become use- 

 ful to the seedling as foliage. These 

 plants, therefore, very soon after coming out of the 

 ground are found actively acquiring the means of further 

 growth, while still using nourishment 

 inherited from the parent plant. 



10. Food. — Along with the incipient 

 plant is sent a store of food in a form 

 easily used, with wdiich its start in 



an independent ca- 

 reer will be made. 

 The amount is as 

 variable as the size 

 of the embryo it- 

 self. It may be 



relatively very large, as seen in the 

 seed of Actsea (Fig. 7). In Fig. 8 

 the embryo is relatively larger than 

 the mass of nutrient material. This 

 example prepares us for the condition 

 seen in the seed of man}' families of 

 plants, where a supply of nutriment 

 separate from the germ itself is never 

 developed (Fig. 9). 



11. Food matter external to the 

 embryo is termed albumen^ or endo- 

 sperm^ and seeds having it are called albuminous seeds. 

 Those lacking albumen are called exalbuminous. 



12. It will readily be seen in most cases that embryos 

 unfurnished with albumen are not in consequence the 

 worse off, for they are of larger size and their tissues are 



Seed of the Purslane, 

 in section, the em- 

 bryo surrounding 

 the reduced albu- 

 men (magnified). 



Section of ihe seed 

 of Actsea, show- 

 ing the minute 

 embryo and the 

 relatively abun- 

 dant albumen 

 (magnified). 



9. Exalbuminous seed 

 of Gynandrop- 

 sis, in section 

 (magnified) . 



