298 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



the embryo proper, while the rest grow out into long tubes, some 

 pushing their way between the cells of the integuments and others 

 extending into the micropyle. 



A reference has already been made to the well-developed sus- 

 pensor haustoria of the Crassulaceae (Mauritzon, 1933) (Fig. 157/). 

 Sometimes their branching is so profuse that it is hardly possible 

 to get a correct idea of it from the study of single sections. In some 

 species of Sedum and Pistoria the haustorial processes pierce the 

 integuments and even extend outside the ovule. 



Walker (1947) has recently given a detailed account of the origin 

 of the massive haustoria of Tropaeohim majus. Here the basal cells 

 of the proembryo divide more actively than the other cells. Such 

 of the cells of this mass as lie on the side away from the funiculus 

 give rise to a long haustorial process which pierces the micropylar 

 part of the integument and finally enters the pericarp. Slightly 

 later, a second protuberance arises from those cells of the mass which 

 lie on the side nearest the funiculus. This, the placental haustorium, 

 grows through the integument and funiculus and reaches up to the 

 point of entry of the vascular bundle of the raphe. 



Perhaps the longest suspensors in angiosperms occur in the 

 Loranthaceae. As mentioned on page 143, in several genera of 

 this family the embryo sacs grow up into the style, and after fertiliza- 

 tion there is a remarkable elongation of the two-rowed suspensor, 

 pushing the terminal cells of the proembryo into the ovary. 



UNCLASSIFIED OR ABNORMAL EMBRYOS 



Although there are several plants whose embryos do not conform 

 to any of the types described previously, only a few need be men- 

 tioned here. 



In all the angiosperms described so far, the first division of the 

 zygote is transverse, but Treub (1885) reported long ago that in 

 Macrosolen cochinchinensis the first wall in the zygote is not trans- 

 verse but vertical. Since then a vertical or nearly vertical division 

 has also been described in several other members of the family, 

 viz., Korthahella (Rutishauser, 1935), Scurrula, Dendrophthoe, 

 (Rauch, 1936; Singh, 1950) (Fig. 170), Lepeostegeres, Amyema, 

 Helixanthera, and Taxillus (Schaeppi and Steindl, 1942). In 

 Balanophora (Zweifel, 1939) the first as well as the second division 

 is vertical and this is probably also true of the third (Fig. 171). In 



