] 50 THE PHENOMENON OF 



greater diameter, arid more bellied out than the suc- 

 ceeding, is the only one which divides no more, and 

 constantly remains sterile. The resting spores of this 

 genus are formed in the swollen end-cells of the subor- 

 dinate rows of links.* 



The .Ramification, like the apical growth, of the many- 

 celled Algse, depends upon a division of the cell into two 

 unlike parts, one of which retains the character of the 

 mother-cell, and the other deviates ; while, however, in 

 apical growth the differing cell belongs to a higher order 

 of cells, in ramification the differing cell returns, on the 

 contrary, to a lower order, since it becomes a cell of the 

 first degree of the first order, that is, the primary cell of 

 a new series of generations. 



Ramification is exhibited in its simplest form in Siro- 

 siphon (Hassallia) and Haplosiphon.\ Particular cells of 

 the rows which form the filament-stem of these Algae, 

 divide in the perpendicular direction into two unlike 

 cells, one of which, mostly larger, remains as a link-cell 

 of the principal filament, while the other, elongating in 

 the horizontal direction, emerges from the stem as a new 

 axis, and then divides again, at right angles to the new 

 axes, into two unlike cells, a new apical cell, and a first 

 link-cell of the branch. The further development of the 

 branch takes place, as in the principal axis, by repeated 

 division of the apical cell, which is followed subsequently 

 by a division of the link-cells. The ramification proceeds 

 in a different way in the Cladopkorce (the branched Con- 

 ferva of the older authors), in which the branches, solitary, 

 or sometimes opposed in pairs, sprout forth from the 

 upper margin of the link-cell, where a bagging out, as it 

 were a new laterally projecting apex of the cell, is first 

 formed, which, by division of the thus enlarged cell into 

 the old and new parts, becomes the first cell of the branch. 



* I am not acquainted with any genus of Alga witli simple filaments 

 formed solely by cell-forming apical growth without subordinate division of 

 the link-cells. Among the ramified Alga?, Batrachospermum forms its stem 

 in this way. 



f Kiitzing, ' Spec. Alg.,' p. 894. 



