ALGAE.— CHARACEAE. 6l 



branches elongate by apical growth and form numerous transverse septa. The lower- 

 most of these cells swell into a roundish shape and form the secondary head-cells, to which 

 are attached' the cylindrical filaments whose disc-shaped cells arc the mother-cells 

 of the spermatozoids (Fig. 39 and Fig. 36, B, C, D, E). 



The antheridia of Chafafragt/h are formed by the metamorphosis of the lateral rays 

 (leaflets) which form the innermost row on a leaf (primary ray), and the development 

 advances on it downwards, as Fig. 41 shows. The sequence in cell-formation and the 

 growth are the same in all important respects as those of Nitella ; the flask-shaped 

 pedicel-cell is here set on a small cell wedged in between the cells of the cortex, the 

 central cell of the basal node of the leaflet, which Braun says occurs even in sterile 

 leaves, but which I have not been able to find there. 



Development of the spermatozoids. The whip-shaped filaments in which the spermato- 

 zoids are formed have intercalary as well as apical growth, as is shown by the presence in 

 the middle of young filaments of elongated cells with two nuclei, between which no 

 division wall has yet appeared (Fig. 36, C) ; the longer the filaments grow, the more 

 numerous are the septa, till at last the individual cells are only narrow discs. The 

 further transformation of the contents of these spermatozoid mother-cells proceeds from 



Fig. 40. Development of the oog 

 magn. about 300 times ; 



ium of Nitella flexilis 

 the ' Wendungszellen ' 



the free end of the filament backwards ; the spermatozoids are formed in basipetal order 

 in each filament. The mode of formation has been recently investigated by Schmitz'. 

 The nucleus is changed directly into the body of the spermatozoid ; the peripheral layer 

 becomes thicker and splits up into a thread of nuclear substance which is rolled in- 

 wards in a spiral manner, while the central part of the nucleus grows looser in texture 

 and becomes a colourless vesicle ; the anterior end that bears the cilia is according 

 to Schmitz the only part of the spermatozoid that is formed from the protoplasm 

 surrounding the nucleus, the largest part of it coming, as has been stated, from the 

 nucleus. The spermatozoids begin to rotate before leaving the mother-cells, and 

 escape from them after the breaking up of the antheridium ; the thread-like body 

 of the spermatozoid has 2-3 coils in Nitella, 3-4 in Chara ; the posterior and thicker 

 end encloses some glistening granules. 



The developmetit of the ocgonium has been described at length by A. liraun ; Sachs 

 has also studied it m Nitella flexilis a.ndCharafragilis. — \nlYitella flexilis the oogonium 

 springs from the node of the leaf beneath the antheridium (Fig. -^7, B and C), and begins 

 to appear some time after it. Fig. 40 shows a very young oogonium whose pedicel-cell 



Untersuch. ii. d. Struktur d. Protoplasmas u. d. Zellkerne in Sitzgber. d. niederrhcin. Ges. 13 Juli 

 p. 31 of the reprint. 



