ANGIOSPERMS. 
the embryo-cell completely excludes the possibility of a bi- or pluri-seriate seg- 
mentation of the apical cell. We learn from Hanstein that the mode of formation 
of the embryo of Monocotyledons may be seen remarkably clearly in Alisma. In 
Fig. 402, //, are shown, above the suspensor v, two other cells a {a is formed 
by the division of the cell z; in /) and c lying one over the other, the last of which 
is already divided by a longitudinal and a transverse wall into four cells arranged 
like quadrants of a sphere. A comparison of the stages //— V shows that the 
further development advances first of all in a basipetal direction. A cell w or h, 
the result of intercalary division, which arises at the end of the suspensor next to 
the embryo a c already formed, is especially to be noted. It is from this that the 
root is subsequently developed. Hanstein calls it and the tissue which proceeds 
from it the hypophysis \ Before the body of the embryo undergoes any external 
Fig. 402.— Formation of the embryo of Monocotyledons {Alisma) (after drawings by Hanstein); /— ^'/// various . 
stages of development ; v the suspensor, h the hypophysis, w the region in which the radicle is formed, p the region in 
which the plumule is formed, c cotyledon, b first leaf (VII and VIII much less magnified than the rest ; the dermatogen 
is shaded). / consists of the rudimentary suspensor v, and of the embryo-cell. 
differentiation, its tissue differentiates into a single peripheral layer (shaded in the 
drawing), and a tissue internal to this ; the former is the primary epidermis or 
to the recent literature of the subject : Fleischer, Beitr. zur Embryologie der Monokotylen und 
Dicotylen, Flora, 1874. — Hegelmaier, Zur Entwick, monokotyledoner Keime, Bot. Zeit. 1874; id. 
Vergl. Untersuch, üb. Entwick. dikotyledoner Keime, mit Berücksichtigung der pseudo-monokotylen, 
Stuttgart, 1878. — Solms-Laubach, Ueb. monocotyle Embryonen mit Scheitelbürtigem Vegetations- 
punkt, Bot. Zeitg. 1878. — Treub, Sur l'embryogenie de quelques Orchidees, Amsterdam, 1879. — 
Westermaier, Die ersten Zelltheilungen im Embryo von Capsella Bursa pastoris, Flora, 1876. — 
Famintzin, Embryologische Studien, Mem. de l'Acad. Imp. de St. Petersbourg, ser. 7, t. XXVI, 
1879.] 
^ [According to Famintzin, the cell w or h \s derived, not from the suspensor, but from the 
division of the cell a : this being the case, it is the cell a which must be regarded as the hypophysis. 
If this is so, the hypophysis, in Alisma, contributes more largely to the formation of the embryo 
than in other instances. Possibly this explanation may be applied to all cases in which two 
embryo-cells are said to be present.] 
