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 

 prothallium. 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 

 lyers. The other daughter-cell, which is sunk in the tissue of the prothallium, 

 jlongates whilst the wall of the neck is being formed and projects between 

 ^he 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 

 >rocesses the archegonium of Equisetum resembles that of Ferns, the only dif- 

 jrence being that in the former the canal- cell does not occupy the whole length 

 >f the neck (Janczewski). The four upper long cells of the neck curve radially 

 mtwards, when the canal of the neck is being formed, like a four-armed anchor, 

 [mmediately after fertilisation the canal of the neck closes, the oosphere, and which 

 ias now become the oospore, enlarges, and the cells of the wall of the ventral 

 )art 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 

 inclined to the axis of the archegonium, and is followed, according to Hof- 

 leister, in each of the two cells by a division-wall placed perpendicularly to the 

 irst. The embryo appears to be composed of four cells arranged like the quarters 

 >f a sphere. The same author states that the foot arises from the lower quarter, 

 le 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 

 ;ell of the first root arises from an inner cell of the tissued 



* [On the Embryology of Equisetum see Sadebeck, Jahrb. f. wiss. Bot. XI. 1878, and also in 

 Jchenk's Handbuch, III. The embryology of Equisetum closely resembles that of Ferns (see infra, 

 ). 426). The oospore divides by successive bipartitions into eight segments : of the four octants 



totming the upper (epibasal) half of the embryo, one gives rise to the stem, two give rise to 

 le first leaf (cotyledon), and one gives rise to the second leaf: of the four octants forming the 



lower (hypobasal) half of the embryo, two give rise to the foot, one disappears, and the remaining 

 )ne, which is diametrically opposite to the stem-octant, gives rise to the root.] 



