548 THE STRUCTURE OF ECONOMIC PLANTS 



Following fertilization, the zygote undergoes a series of trans- 

 verse divisions which result in the formation of a linear series of 

 cells. (Fig. x89, A.^ The basal cells of the proembryo form the 

 suspensor, and vertical divisions of the terminal cells result in the 

 development of an enlarged spherical structure which becomes the 

 embryo. Early in its differentiation, there is a blocking off of 

 definite histogens so that the initials of the dermatogen, the 

 periblem, and the plerome can be determined; and development 

 of the epidermis, cortex, and stelar structures then follows. (Fig. 

 i.S^, D, E, F.^ The embryo soon becomes bilobed; and subsequent 

 growth of these lobes leads to the formation of the two cotyledons, 

 while elongation and differentiation of the axis of the embryo result 

 in the production of the hypocotyl and radicle. (Fig. 2.S<^, G.) 

 During ontogeny, the endosperm develops rapidly and at maturity 

 it completely surrounds the embryo. (Fig. 175, A.^ 



LITERATURE CITED 



I. Artschwager, E., "Anatomy of the potato plant, with special reference to 

 the ontogeny of the vascular system." Jour. Agr. Res. 14: iii-z5i, 1918. 

 1. , "Studies on the potato tuber." Jour. Agr. Res. 2j: 809-836, 19x4. 



3. AuGUSTiN, Bela, Historisch-kritische und anatomisch-entwicklungsgeschichtliche 



Untersuchung iiber den Paprika, Adolph Rosner, Nemetbogsan, 1907. 



4. Berthault, p., "Recherches botaniques sur les varietes cultivees du Solanum 



tuberosum et les especes sauvages de Solanum tuberiferes voisins." Ann. 

 Set. Agron. 28: 1-59, 87-143, 173-116, 148-191, 1911. 



5. Bhaduri, p. N., "Studies on the female gametophyte in Solanaceae." Jour. 



Ind. Bat. Sac. 14: 133-150, 1935. 

 6. , "Studies on the embryogeny of the Solanaceae. I." Bot. Ga^. 98: 



183-195, 1936. 

 Clark, C. F., "Development of tubers in the potato." U. S. Dept. Agr. Bull. 



9^8, 1911. 

 Cooper, D. C, "Macrosporogenesis and the development of the macrogame- 



tophyte of Lycopersicon esculentum." Am. Jour. Bot. 18: 739-748, 193 1. 

 Crafts, A. S., "Sieve-tube structure and translocation in the potato." Planf 



Phys. 8: 81-104, 1933. 

 Dorsey, M. J., "A note on the dropping of flowers in the potato." Jour. 



Heredity 10: 116-118, 1919. 

 East, E. M., "Some essential points in potato breeding." Conn. Agr. Exp. 



Sta., Ann. Rep., 419-447, 1907-1908. 

 Esmarch-Bromberg, F., "Beitrage zur Anatomie der gesunden und kranken 



Kartoffelpflanze." Landw. Jahrh. ^4: i6i-i66, 1919. 

 Ferguson, M. C, "A cytological and a genetical study of Petunia — I." 



Bull. Torr. Bot. Club ^4: 657-664, 1917. 



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