SEEDS. 13 



to the embryo in early stages of germination. 

 Cf. Haberlandt, Physiologische Pflanzenanatomie, 

 p. 288 et seq. 



IV. Peculiar cases of plant dissemination. Cf. Ber- 



thoud, Botanical Gazette, XVII (1892), p. 321. 

 V. Identification of species by means of seeds. An 

 interesting application will be found in the deter- 

 mination of weed seeds of frequent occurrence in 

 grass and clover seed. Cf. Beal, Grasses of North 

 America, I, p. 215. 



REVIEW AND SUMMARY. 



The seeds we have studied have been selected from 

 three great classes of plants. To the first class belong 

 the bean, castor oil, and other plants, the seeds of which 

 have two cotyledons ; to the second, wheat, Indian corn, 

 and, in general, all plants with one cotyledon ; and to the 

 third, pines and their allies, many of which have more 

 than two cotyledons. The distinctions between these 

 classes are in many respects fundamental, so that an 

 examination of the seed of a given plant is generally suffi- 

 cient to enable us to determine its class in the vegetable 

 kingdom. 1 



Furthermore, we have found that there are more re- 

 stricted groups of plants, called families, the seeds of 

 which are in many cases, though not in all, so nearly 

 identical in structure as to indicate at once their family 

 relationship. The squash, melon, and cucumber belong 

 to one of these families ; the tomato, egg plant, and stra- 

 monium to another, and so on. We conclude, therefore, 



1 Seedless or " cryptogamic " plants will be studied later. What is 

 said in the present chapter and those immediately following applies to 

 the higher or seed-bearing plants, including Gymnosperms. 



