588 
PHANEROGAMS. 
[A row of cells is thus formed, from the lowermost of which, usually a spheroidal 
cell which we may term the embryo-cell, the greater part of the embryo is in most 
cases formed; but in many cases (in many Papaveraceae and Caryophyllaceae, in 
Asclepias, Cuscula, Nicotiana, Viola, and others, amongst Dicotyledons, and com- 
monly among Monocotyledons) the Iwo end cells of the row form the chief part 
of the embryo. Hanstein considered that the presence of two embryo-cells was 
characteristic of Monocotyledons, but Hegelmaier has found that a single embryo- 
cell occurs in this group {e.g. Ornithogalum natans), and that two embryo-cells 
frequently occur in Dicotyledons, as mentioned above. The upper cells of the 
row form the Suspensor. In some cases {Glauciufn) the cells of the suspensor 
undergo longitudinal divisions, and it consists consequently of several rows of cells. 
Usually the lowest cell of the suspensor, the hypophysis, contributes to the forma- 
tion of the embryo. In the Graminese the cells of the suspensor divide and form 
a multicellular appendage at the radicular end of the embryo {Keimanhang, Han- 
stein) ; when the primary root begins to elongate this mass of cells is split off and 
it forms a sort of sheath (coleorhiza) to the young root.] The suspensor usually 
remains short (Fig. 400) ; sometimes, as in Funkia, its basal cell swells up into a 
globular form (Fig. 399) ; in other cases (as, according to Hofmeister, in Loranthus) 
the oospore lengthens before division, and penetrates to the considerably enlarged 
base of the long tubular embryo-sac. In those Dicotyledons where the endosperm 
is formed only at certain lower parts of the embryo-sac by division, a similar elon- 
gation of the oospore is usual, although not to so great an extent {e.g. Pedicular is, 
Calalpa, Labiatae). In the embryo-cell a longitudinal or only slightly oblique 
division-wall first of all makes its appearance, indicating the commencement of the 
formation of the embryo (see also Fig. 15, p. 18). As this is followed by rapidly 
repeated divisions, a spherical or ovoid mass of small-celled tissue is produced, from 
which the first foliar structures, the cotyledons, subsequently arise, while the rudi- 
ment of the first root may be observed in the differentiation of the tissue at the 
boundary-line of the suspensor and embryo. The first cells of the embryo are 
not unfrequently disposed as if they had resulted from oblique divisions of an 
apical cell in two or three directions (Fig. 400 C), a supposition which is com- 
pletely supported by the oblique position of the first septum in the embryo-cell; 
in Rheum I also found the apex of young embryos to present an appearance which 
suggested the existence of a three-faced apical cell. According to Hanstein's new 
and prolonged researches, the process is, nevertheless, different ; he asserts that the 
first longitudinal wall, even when it stands obliquely to the last transverse wall, is 
still in the median plane of the body of the embryo which is being formed, and 
is frequently at right angles to the last transverse wall, and therefore in the axis 
of growth of the suspensor \ The formation of this median longitudinal wall in 
^ The description in the text is taken from Hanstein's preliminary publications (Monatsberichte 
der niederrhein. Gesellsch. für Natur- und Heilkunde, July 15 and August 2, 1869), as well as from 
more detailed communications in letters. Professor Hanstein has also had the kindness to allow me 
the sight of a number of drawings ; and, with his permission, the figs. 402-405 are copied from 
them. I have also had the opportunity, in the summer of 1869, of seeing preparations of Hanstein's 
similar to Fig. 403. Compare also Hanstein, Botanische Abhandlungen, Heft I, for a more detailed 
description of the development of the embryo in Monocotyledons and Dicotyledons, [See also 
Quart. Journ. Micr. Soc. 1873, p. 51. The following are some of the more important contributions 
