106 MORPHOLOGY OF ANGIOSPERMS 



and sometimes the antipodals. This haustorial tube was ob- 

 served to begin its development at different stages in the history 

 of the sac, sometimes being evident in the two-nucleate stage 

 of the sac, sometimes not having begun in the seven or eight- 

 nucleate stage. 



One of the strangest cases is that of Trapella, as described 

 by Oliver. 21 In this the innermost megaspore of a row of four 

 becomes extremely elongated, penetrates the chalaza, and 

 divides longitudinally, the two cells being very active, as indi- 

 cated by their contents and numerous starch grains. In this 

 form the synergids enlarge and persist on the apex of the sac 

 (Fig. 32)/ 



Among the Scrophulariaceae, such as Pedicularis, Rliinan- 

 thus and its allies, etc., Tulasne, Hofmeister, Tschirch, Schlot- 

 terbeck, and others have described the numerous vermiform 

 tubes that develop from the embryo-sac and " ruminate " the 

 integument and destroy its tissue, although they did not recog- 

 nize their origin ; and similar tubes have been found in certain 

 Labiatae. Recently Balicka-Iwanowska 68 has investigated the 

 embryo-sacs of many Scrophulariaceae, as well as other allied 

 Sympetalae, and has discovered a remarkably constant occur- 

 rence of haustorial outgrowths from the sac at both micropylar 

 and chalazal ends, filled in later by endosperm cells. The 

 common case is for the broad micropylar end of the sac to de- 

 velop four prongs, and for the narrower chalazal end to fork, 

 as seen not merely among Scrophulariaceae, but also among 

 Utriculariaceae, Pedaliaeeae, and Plantaginaceae. The devel- 

 opment of these haustoria is related to the thickness of the 

 integument, which in these groups seems to be a source of nutri- 

 tive supply. There are all stages in the development of the 

 haustoria, but the general tendency in this region of the Sympet- 

 alae is very marked. A striking case is that of the well-known 

 Torenia asiatica, mentioned above, in which the sac does not 

 develop outgrowths, but protrudes bodily beyond the micropyle, 

 touching the funiculus, and even reaching the ovary wall. All 

 of these haustorial outgrowths are supplied with active endo- 

 sperm cells or nuclei. 



It is stated that all species of Campanulaceae (Balicka- 

 Iwanowska 68 ), Lobeliaceae (Billings 100 ), and Stylidaceae 

 (Burns 85 ) develop both micropylar and chalazal haustoria, and 



