THE ANGIOSPERMAE 



1415 



about these synergid haustoria or to distinguish them exactly from other 

 cases in which the whole micropylar part of the embryo sac, including the 

 oosphere, extends itself upwards into the 

 micropyle, or from still other cases in 

 which the haustorial cells are either 

 endosperm cells or cells of the em- 

 bryonal suspensor, which may develop 

 in a similar manner and have very much 

 the aspect of synergid cells, although 

 naturally formed later and after the dis- 

 appearance of the synergidae (Fig. 1306). 



True synergid haustoria arise from 

 the free apices of the embryo sacs in 

 some Santalaceae (see below) and are 

 often complexly branched. 



The synergidae have generally a 

 limited period of usefulness and break 

 down after fertilization. They some- 

 times persist, however, the most re- 

 markable case being that of Trapella, 

 where they enlarge and remain active 

 as haustoria even when the embryo is 

 mature. (See Fig. 1315.) 



Micropylar outgrowths of the embryo Fig. 1206. —Lobelia cUffordiana. Two 

 sac itself, of a haustorial nature, are not uppermost endosperm cells pro- 



• . . , jectmg towards micropvle and 



uncommon. The classic case is that ot simulating the appearance of the 



Torenia (Scrophulariaceae), where the synergidae xn Calendula (Fig. 1305 



\ / '\ A). {After Bilhngs.) 



nucellus breaks down early and the 



upper part of the embryo sac protrudes through the micropyle and swells 

 out like a balloon (Fig 1307 B). In the Utriculariaceae similar outgrowths 

 are generally to be found. The ovules are unitegminous and anatropous. 

 After the breakdown of the nucellus the embryo sac extends out of the 

 wide micropyle and impinges upon an area of nutritive tissue at the base 

 of the funicle, where it joins the placenta (Figs. 1307 and 1308). This 

 tissue subsequently breaks down and after fertilization the haustorium 

 is invaded by endospermal nuclei which enlarge and fuse, the haustorium 

 wall separating it from the placenta breaks down and the cytoplasm and 

 nuclei of both structures form a common mass, while the embryo is devel- 

 oping. A similar but smaller haustorium is also formed at the chalazal 

 end, also in connection with a mass of nutritive cells (Fig. 1307 C). 



In Phaseulus the upper portion of the embryo sac breaks through the 

 nucellar tissue and occupies the micropyle, but does not extend beyond it. 

 In Galium hicidnm the whole sac appears to leave the ovule through the 

 micropyle and " creeps " into the narrow space between the ovule and the 

 ovary wall. This leads us to the extraordinary state of affairs in the Loran- 

 thaceae and Santalaceae in which no ovules are organized and the embryo 



