DIODIA VIRGINIANA 49 
of which is ultimately covered by the strophiole. Certain features 
of special interest attach to this organ which will now be described. 
In the first place, the supply of vascular tissue to the ovule is 
confined to the strophiole. A single strand of the same passes 
through the funicle and upon reaching the strophiole divides, 
sending one branch, the chief one, to the chalazal region of the 
strophiole, the other toward the micropylar region (a and a’, figs. 
2, 8,9). The chalazal branch (a) presents at its extremity a sharp 
turn towards the spot at which lies the archesporium. 
Secondly the limit of the strophiolar tissue is sharply defined 
by the presence of a plate of brown-walled cells (sf. in the figures), 
having the same cytological characters as the epidermal cells of 
the integuments, which also become brown. In the young ovule 
the strophiolar plate is not to be seen, and has its origin at about 
the time the embryo-sac reaches its definitive condition, in scat- 
tered cells which marked the position of the plate, and which in- 
crease in number until the sheet of tissue is complete. When 
this takes place there are no fenestrations in the plate excepting 
a sometimes smaller one at the extremity of the chalazal branch 
of the vascular supply. It ultimately becomes continuous with 
the epidermis (epi, fig. 9) and thus the ovule exclusive of the stroph- 
iole comes to be completely surrounded by a sheath of cells with 
scanty plasmatic content, and deep brown walls. 
In the third place the strophiole is characterized by the occur- 
rence of a large number of excretory cells which become filled 
with raphides. When the seed is mature the strophiole carries a 
heavy load of calcium oxalate. As many as two hundred of the 
raphide cells have been counted. The remainder of the tissue is 
composed of cells which do not differ materially from the paren- 
chyma of the integument. From the foregoing facts, it must be 
evident that the strophiole is the seat of special metabolic activity, 
during the growth of the embryo and endosperm, and that the 
strophiolar plate is of no special hindrance to the passage of proper 
food materials used by the embryo and endosperm. 
ARCHESPORIUM AND EMBRYO-SAC 
The archesporium is laid down in certain hypodermal cells of 
the nucellus of any early age. No tapetal cells are cut off, nor is 
Mo. Bot. Garzea 
E KS NANA er NA REN NO 
