FECUNDATION ; HETEROGAMETES. 



of which only one is borne in each antheridium, are, according to 

 Pringsheim ('58, p. 297), almost entirely colorless, with but a faint 

 greenish hue ; each bears at the anterior end two cilia, one extending 

 backward during the progressive motion of the cell. In the absence 

 of a chromatophore the spermatozoid of Coleochcete differs from that 

 of (Edogonium, in which the chlorophyll undergoes a transformation 

 in the male gametes, and in this respect it foreshadows 'the develop- 

 ment of the sperm in higher plants. 



The oogonium is also developed from the end cell of a branch. 

 It is recognized first by the presence of a beak at the distal end of the 



cell, which soon becomes the 

 neck of the flask-shaped organ 

 (Fig. 32, C, D). In the neck 

 dense colorless cytoplasm accu- 

 mulates which contains one or 

 more large vacuoles. In the 

 basal or ventral portion are sit- 

 uated the nucleus, a large vac- 

 uole, and a laterally placed 

 chloroplast. The neck now 

 increases in length with an ap- 

 parent increase in the quantity 

 of its cytoplasm, the ventral 

 portion remaining unchanged. 

 As soon, however, as the neck 



h as reached its definitive size, a 

 . 



transformation takes place in 

 the ventral part of the oogo- 

 iiium ; the chloroplast leaves its lateral position, passes down and applies 

 itself closely to the bottom of the organ (Fig. 33, E). It has increased 

 appreciably in size and contains two pyrenoids. The oogonium opens 

 probably by the gelatinization of the end wall of the neck. As soon 

 as the organ opens the cytoplasm contracts into the basal portion to form 

 the egg-cell. Whether a part of the cytoplasm in the neck is thrown 

 off cannot be stated positively, but there is no reason to believe that 

 this occurs. Both Jost and Oltmanns accord in the opinion that no 

 cytoplasm is expelled when the oogonium opens, while Pringsheim 

 speaks of the extrusion of a colorless substance only, which disor- 

 ganizes at once. The expulsion of a small quantity of mucilaginous 

 substance, or even cytoplasm, is utterly without important significance, 

 as the nucleus of the oogonium does not divide previously to fecunda- 



FIG. 32. Development of sexual organs in Coleochcete 

 pulvinata. (After Oltmanns.) 



A, B, development of antheridium. 

 C,D, two young stages of the osgonium. 



