THE EMBRYO 291 



into the endosperm, where it is surrounded by cells containing 

 abundant food materials. Especially striking examples of an 

 elongated proembryo are seen in the long and narrow embryo sacs 

 of the Sympetalae and have been fully described and illustrated in 

 Haberlea (Glisic, 1928), Gratiola (Glisic, 1933), Utricularia (Kausik, 

 1938), and several other plants. In later stages the narrow basal 

 portion of the proembryonal tube becomes crushed and obliterated, 

 while the broader terminal portion, which is destined to give rise to 

 the embryo proper, becomes favorably placed in the central mass of 

 endosperm. In Salvia splendens (Carlson and Stuart, 1936) not 

 only does the proembryonal filament elongate downward into the 

 endosperm but it also protrudes in the opposite direction, so that a 

 portion of it comes to lie inside the endosperm haustorium produced 

 at its micropylar end. 



In several plants the suspensor cells show a pronounced increase 

 in size or give rise to prominent haustorial structures which pene- 

 trate between the cells of the endosperm and encroach upon the 

 surrounding tissues of the ovule. The range of variation in this 

 respect may be illustrated by referring to a few families and genera 

 which are of special interest from this point of view. 



Guignard (1882) gave a very detailed account of the modifications 

 of the suspensor in the Leguminosae. In several members of the 

 subfamily Mimosaceae and of the tribe Hedysareae, a suspensor is 

 virtually absent and the proembryo forms a spherical or ovoid mass 

 of cells without any differentiation. Soja, Amphicarpaea, and Tri- 

 folium have a rudimentary suspensor consisting of three or four 

 cells. In Pisuw, and Orobus, which have a suspensor consisting of 

 two pairs of cells arranged in a crosswise fashion, the two micro- 

 pylar cells are elongated but the next two are more or less spherical ; 

 all four of the cells are multinucleate (Fig. 1Q5E,F). In Ocer 

 (Fig. 165G) and Lupinus (Fig. 165A-C) the suspensor is much 

 longer. In L. pilosus (Fig. 165A) some of the cells become detached 

 from one another and lie free in the micropylar part of the embryo 

 sac. In Ononis (Fig. 1657) the suspensor consists of a filament of 

 large and conspicuous cells which are packed with food materials. 

 In Medicago and Trigonella it is more massive, and Phaseolus (Fig. 

 165D) is similar except that here the distinction between the cells 

 of the suspensor and embryo proper is not very sharp. Finally, in 



