272 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



(ii) The basal and terminal cells both contribute to the de- 

 velopment of the embryo Asterad type 



II. The terminal cell of the two-celled proembryo divides by a 

 transverse wall — 



1. The basal cell plays only a minor part or none in the subse- 

 quent development of the embryo — 



(i) The basal cell usually forms a suspensor of two or more 



cells Solanad type 



(ii) The basal cell undergoes no further division, and the 

 suspensor, if present, is always derived from the terminal 

 cell Caryophyllad type 



2. The basal and terminal cells both contribute to the develop- 

 ment of the embryo Chenopodiad type 



Crucifer Type. As mentioned in Chap. 1, the embryo of Capsella 

 bursa-pastoris was among the first to receive detailed attention. 

 Subsequent to the classical researches of Hanstein (1870) and 

 Famintzin (1879), Soueges (1914, 1919) has made a still more 

 thorough study of its embryogeny. The first division of the zygote 

 is transverse resulting in a basal cell cb and a terminal cell ca (Fig. 

 145 A, B). The former divides transversely and the latter divides 

 longitudinally, resulting in a J_ -shaped proembryo composed of four 

 cells (Fig. 145C-E 1 ). Each of the two terminal cells now divides 

 by a vertical wall lying at right angles to the first, so as to result in 

 a quadrant stage (Fig. 145/). The quadrant cells in turn become 

 partitioned by a transverse wall, so as to form octants (Fig. 145K, 

 L). Of these the lower four are destined to give rise to the stem 

 tip and cotyledons and the upper four to the hypocotyl. All the 

 eight cells divide periclinally (Fig. 145M,iV). The outer deriva- 

 tives form the dermatogen, while the inner ones undergo further 

 divisions to give rise to the periblem and plerome initials (Fig. 145 

 O-Q). 



Meanwhile, the two upper cells ci and cm, of the four-celled pro- 

 embryo (Fig. 1452)) divide to form a row of 6 to 10 suspensor cells 

 (Fig. 145F-K) of which the uppermost cell v becomes swollen and 

 vesicular and probably serves a haustorial function. The lowest 

 cell h functions as the "hypophysis" (Fig. 145A0- Although at 

 first similar in shape to the other cells of the suspensor, it soon be- 

 comes somewhat rounded at the lower end and divides transversely 

 to form two daughter cells (Fig. 1450), each of which undergoes two 



