EMBRYO SAC AND EMBRYO OF PENTSTEMON 



SECUNDIFLORUS 



CONTRIBUTIONS FROM THE HLILL BOTANICAL LABORATORY 248 



Arthur T. Evans 

 (with PLATE XIl) 



Two genera of the Scrophulariaceae were the first plants in 

 which the development of the embryo sac and the embryo were 

 correctly investigated. In 1851 Hofmeister (8), working on 

 Lathraea squamaria and Pedicularis sylvalica, proved that the 

 embryo was formed as a result of the fertilization of the egg, and 

 not from the end of the pollen tube as was believed by Schleiden 

 and his followers. Deecke (5) in 1855 reinvestigated Pedicula- 

 ris sylvatica. He insisted that Hofmeister was wrong and that 

 the embryo really did develop from the end of the pollen tube. 

 He was supported in his assertions by Schacht (ii). Later, how- 

 ever, Hofmeister (9) proved that what Deecke really saw was 

 the proembryo. In his paper on Lathraea and Pedicularis, Hof- 

 meister discusses the beginning of the endosperm and the 

 haustoria. No further work of importance was done upon the 

 Scrophulariaceae until 1874, when Chatin (3) studied the devel- 

 opment of the ovule and the seeds in a number of genera. Four 

 years later Vesque (14) worked on the embryo sac of a number of 

 families, among which were included several of the Scrophulariaceae. 

 Even as late as his publication of this paper Vesque believed that 

 Schleiden's theory of the formation of the embryo was correct, 

 and criticized Hofmeister's interpretation as inaccurate. 



One of the best contributions to our knowledge of the embryo 

 sac situation in this family is by Balicka-Iwanowska (2) in 1899. 

 The account includes a study of a number of families of the Sym- 

 petalae, but deals especially with several genera of the Scrophu- 

 lariaceae, particularly taking up the question of nutrition in the 

 embryo sac. The haustoria are believed to have an absorptive 

 power, and thus conduct nourishment into the embryo sac, the 



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