108 



MORPHOLOGY OF ANGIOSPERMS 



that often finger-like processes are put out at the side or base 

 of the sac, extending toward the vascular bundles ; and in Sty- 

 lidaceae, immediately after the entrance of the pollen-tube, the 

 micropylar part of the embryo-sac grows out into an enormous 

 haustorium much larger than the rest of the sac (Fig. 50). As 

 a result of his investigations of Polypompholyx and Byblis, 

 Lang 91 not only discovered conspicuous haustoria, but used this 

 character, along with others, such as the nucellus with a single 



row of axial cells, the tapetum de- 

 rived from the single integument, 

 and the united petals, to remove 

 these genera from the arcbiclilamy- 

 deous Droseraceae to the sympetalous 

 Lentibulariaceae. 



The whole subject of the mecha- 

 nism for the nutrition of the embryo- 

 sac deserves more detailed attention 

 than it has received. In his study of 

 the fleshy plants, D' Hubert, 33 on the 

 basis of the appearance and disap- 

 pearance of starch, concludes that the 

 antipodals nourish the sac before fer- 

 tilization, the synergids nourish the 

 nuclei of the pollen-tube and then 

 the nucleus of the egg at the time 

 of fertilization, and the polar nuclei 

 nourish the fertilized egg and give 

 rise to the endosperm (Fig. 51). 

 Such details may prove true fur the 

 Cactaceae and other fleshy plants.* 

 but the larger field is to be traversed 

 first, which embraces all of the mor- 

 phological structures used in obtaining nutritive supplies fur 

 the structures within the embryo-sac, both before and after fer- 

 tilization. Just what mechanism supplies what structure is a 

 subordinate detail and very difficult to prove, besides being an 

 exceedingly improbable division of labor among structures so 



* D'Hubert concludes that starch is characteristic of fleshy plants, but 

 there is a. large display of standi in Astilbe (Webb ul ) and Galium (Lloyd 105 ), 

 and doubtless in many other non-fleshy plants. 



Fig. 51 



Phyllocactus. Starch dis- 

 appearing from antipodals and 

 accumulating in other portions 

 of the embryo-sac; a, antipo- 

 dals; e, egg-apparatus;/?, polar 

 nucleus ; x 6GG. — After D'llu- 



BERT.33 



