EQUISETINE.E. 
395 
Hofmeister terms an undulating Float, Schacht a thin-walled vesicle of proto- 
plasm, and which contain granules of starch and sap (compare with Ferns and 
Isoeteae). 
The Archegonia are developed from single superficial cells of the anterior 
margin of the thick and fleshy lobes of the female prothallium. As the tissue 
of the prothallium beneath them continues its growth, the archegonia come, as 
in Pellia, to stand on its upper surface. The mother-cell of the archegonium, 
after it has become much curved, divides by a wall parallel to the surface of the 
prothalHum. From the outer of the two daughter-cells is formed the neck, con- 
sisting, at a subsequent period, of four parallel rows each of three cells. Of these, 
the four upper cells become very long ; the four middle ones remain shorter ; the 
four lower ones scarcely elongate at all, and contribute by their multiplication, 
like the cells of the prothallium which surround the central cell, to the formation 
of the wall of the ventral part of the archegonium, which consists of one or two 
layers. The other daughter-cell, which is sunk in the tissue of the prothallium, 
elongates whilst the wall of the neck is being formed and projects between 
the four rows of cells constituting it. This projection is then cut off by a septum 
from the lower large portion of the cell. Of the two cells thus formed, the 
former is the single canal-cell of the neck, and the latter is the central cell of 
the archegonium. The central cell is divided again into two, the upper being 
the ventral canal-cell, the lower contracting and forming the oosphere. In these 
processes the archegonium of Equisetum resembles that of Ferns, the only dif- 
ference being that in the former the canal- cell does not occupy the whole length 
of the neck (Janczewski). The four upper long cells of the neck curve radially 
outwards, when the canal of the neck is being formed, like a four-armed anchor. 
Immediately after fertilisation the canal of the neck closes, the oosphere, and which 
has now become the oospore, enlarges, and the cells of the wall of the ventral 
part of the archegonium which surrounds it begin rapidly to multiply. 
Development of the Asexual Generation (Sporophore) of Equisetum. The 
formation of the embryo from the oospore is the result of divisions, the first of which 
is inclined to the axis of the archegonium, and is followed, according to Hof- 
meister, in each of the two cells by a division-wall placed perpendicularly to the 
first. The embryo appears to be composed of four cells arranged like the quarters 
of a sphere. The same author states that the foot arises from the lower quarter, 
the rudiment of the first shoot from one of the lateral ones, turning upwards 
immediately afterwards and producing as the rudiment of the first leaf a pro- 
jecting girdle, which then grows out into three teeth (Fig. 277 B). The apical 
cell of the first root arises from an inner cell of the tissued 
^ [On the Embryology of Eqtdsehcm see Sadebeck, Jahrb. f. wiss. Bot. XI. 1878, and also in 
Schenk's Handbuch, III. The embryology of Equhettmi closely resembles that of Ferns (see infra, 
p. 426). The oospore divides by successive bipartitions into eight segments : of the four octants 
forming the upper (epibasal) half of the embryo, one gives rise to the stem, two give rise to 
the first leaf (cotyledon), and one gives rise to the second leaf : of the four octants forming the 
lovi^er (hypobasal) half of the embryo, two give rise to the foot, one disappears, and the remaining 
one, which is diametrically opposite to the stem-octant, gives rise to the root.] 
