Chapter XX. 



What Seeds are and how they are Produced. 



About 150,000 different kinds of plants produce seeds. A 

 seed may be defined as a young plant and its reserve-food- 

 material enclosed within a normally protective layer. Some- 

 times the food-material is deposited beside or around the 

 plantlet, as in the seeds of Indian corn and wheat. Again the 

 food-material may be collected in the plantlet itself, giving to 

 it a white, meaty appearance, and pumpkin and bean seeds are 

 of this structure. It is a mistake to say that plants grow from 

 the seed, or rather it is a half-truth, for the question is whence 

 did the plantlet come that is already present in the seed and 

 needs only to renew its development when the seed germinates? 

 This can be answered in a word. Leaving out of considera- 

 tion some abnormal or peculiar conditions of development, it 

 may be said that all plantlets in seeds arise from eggs. The 

 next question is whence comes the egg from which the plantlet 

 in a seed develops? The reply is, that the egg, as in all other in- 

 stances, is produced in the body of a female plant. Still an- 

 other question where is one to look for the female plant of a 

 rose or willow, or any other seed-producing species? To this 

 inquiry the answer is, the female, like all other females in the 

 great series of terrestrial plants, develops from a spore. Again, 

 one inquires, where is the spore to be sought? To this is the 

 response that it is formed in the young ovule or rudimentary 

 seed, occurring as a more or less oval, cylindrical or elongated 

 cell in the centre of the seed-rudiment. 



What then is the seed-rudiment? It is a spore-case which 

 produces at its centre the single, large, thin-walled spore. In 

 seed-plants such a spore is called an embryo-sac and it may 

 easily be found by opening young pine-seeds in cones not more 

 than twelve months old. Unlike the large-spores of the smaller 



