ANalOSPEEM^ 185 



size as to make its way out of the embryo sac through the mioro- 

 pyle and to ramify in the interior of the ovary and the tissue 

 of the placenta. In some Dicotyledons a somewhat similar 

 behaviour is found. In such cases it recalls physiologically as 

 well as morphologically the foot of the Ferns and their allies, 

 absorbing nutriment for the support of the embryo. 



The suspensor contributes a cell to the formation of the 

 embryo in a manner to be described below. 



The epibasal cell, often termed the embryo cell, divides very 

 differently. In it three walls are formed successively at right 

 angles to each other, dividing it into eight octants. The octants 

 in this group, it will be noticed, all proceed from the epibasal 

 cell only and not from the whole zygote as in the Ferns, &c. 

 The recent separation of the hypobasal cell causes the epibasal 

 one not to be a sphere as is the zygote, so that the octants next 

 the suspensor are flattened somewhat and abut upon the latter 

 in a somewhat truncated fashion. The subsequent divisions differ 

 somewhat in the Dicotyledons and the Monocotyledons. In the 

 former group the anterior octants give rise to the upper por- 

 tion of the axis, but the posterior ones only form the hypo- 

 cotyl, the primary root being formed from the last cell of the 

 suspensor, the so-called hypophysis. In the latter group this 

 cell gives rise to the growing point of the laterally produced 

 stem, and the root originates in the segment of the hypophysis 

 next to the rest of the suspensor. 



When the octants have been formed, the next step in the 

 development is the formation of the dermatogen by walls 

 parallel to the surface of the embryo. At first the dermatogen 

 is incomplete, the periclinal walls only being formed in the 

 octants. Soon it is continued across the hypophysis, "which 

 has by this time grown up in a slightly bulging fashion at the 

 base of the embryo (figs. 936 and 937). Of the cells so formed 

 from the hypophysis the internal one gives rise to the periblem 

 of the root, while the latter forms its dermatogen, which soon 

 becomes many-layered and constitutes the root cap. The fur- 

 ther growth of the embryo soon gives rise to the three systems 

 of tissue already described, the dermatogen, periblem and 

 plerome. 



In the Monocotyledons the terminal cotyledon is developed 

 from the octants, the hypophysis dividing to form a row of cells, 

 of which the anterior ones give rise to the stem while the pos- 

 terior one forms the root, as the whole hypophysis does in 

 Dicotyledons. The order of division of cells is very similar, 



