the Seed in the Alsinoideae. 
3i 
of the carpels on the flower rudiment, a conical portion forming the extreme 
apex of the latter remains, and it is this axile apical portion which grows on 
in the centre of the carpels, forming the columella. The growth of the 
columella is at first more rapid than that of the carpellary whorl. The 
ovules arise on it in basipetal succession, and the ovular outgrowths appear 
on the top of the columella before it is enclosed by the carpels. The 
nucellus first consists of a one-layered epidermis and some hypodermal 
cells. As it increases in length by anticlinal divisions of these cells 
a larger hypodermal cell is soon distinguishable (PI. V, Fig. 2, mi) ter- 
minating the axile row of the nucellus. This cell is the primary megaspore, 
and as Vesque found for Stellaria Holostea , it becomes the functional mega- 
spore without further tangential divisions. Anticlinal divisions now appear 
in some of the epidermal cells of the nucellus, which if occurring over the 
megaspore, may simulate tangential divisions of the latter (PI. V, Figs. 3 
and 5). In Stellaria idiginosa in two cases, exceptions to this rule were 
seen (Figs. 1 and 2, t. and mi) ; but in Fig. 2 the apparent tapetum may be 
derived from the epidermal layer, the section being possibly oblique. 
As the primary megaspore enlarges, two or three of the cells below it 
in the same vertical row become differentiated from the surrounding tissue 
in size, denser contents, and in larger nuclei (PL V, Figs. 3 and 5, ax. c.), 
and it is at the expense of these cells that the subsequent growth in length 
of the megaspore takes place. 
The cells of the nucellus in immediate contact with the megaspore 
also show larger nuclei and denser contents, simulating sporogenous tissue. 
Some caution is therefore necessary in the interpretation of even slightly 
oblique sections. 
The integuments arise in basipetal succession. 
Embryo-sac. The first division of the nucleus of the megaspore occurs 
before the inner integument encloses the nucellus (PI. V, Fig. 5,e. s.). Sub- 
sequent divisions to the eight-nuclei stage follow in normal sequence 
(Fig. 6, e. s.). Very rapid anticlinal, and less rapid periclinal, divisions 
of the epidermal layer of the nucellus follow (PI. V, Fig. 6, per. /.), with the 
result that the embryo-sac becomes sunk in its tissue and is enclosed in four 
or five concentric layers which join on to the axile rows at the base of the 
nucellus (Figs. 6 and 7, per. 1 . and ax. cl). 
Increased anticlinal divisions occur at the apex of the nucellus 
(Fig. 4, ap. nuc . ), also noted by Vesque ( 9 ), who speaks of the ‘ nucellar 
cap.’ The increased periclinal divisions he figures for the ‘ cap ’ were not 
seen, and each layer in every case can be traced all round the periphery of 
the nucellus in all stages of the growing ovule. These cells, at the imme- 
diate apex of the nucellus just under the micropyle, form loose vertical 
rows (Figs. 6, 7, ap. nuc.), the extreme cells of which, just before fertilization, 
are prolonged as papillae into the micropyle (Fig. 13, ap. mic . ). 
