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 archichlamy- 

 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 I 

 nourish the fertilized egg and give 

 rise to the endosperm (Fig. 51). 

 Such details may prove true for 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 for 

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

 tilization. Just what mechanism supplies w r hat 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 starch in Astilbe (Webb 1U ) and Galium (Lloyd 105 ), 

 and doubtless in many other non-fleshy plants. 



FIG. 51.Pkyllocactus. Starch dis- 

 appearing from antipodals and 

 accumulating in other portions 

 of the embryo-sac; a, antipo- 

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

 nucleus; x 668. After D'Hu- 



BERT. 83 



