84 FECUNDATION J HETEROGAMETES. 



In var. erassisepta with uninucleate egg-cells the problem is simpler. 

 The observation of the process in this form in connection with var. 

 bratinii was fortunate, as it must have served as a control in the 

 interpretation of the phenomena in the multinucleate eggs. If the 

 observations of Klebahn be correct, var. braunii represents the only 

 authentic case among the algae of a normal sexual union of a single 

 male and female nucleus in an egg-cell containing several nuclei of 

 apparently equal morphological value. 



FUCACE^. 



In certain respects the sexual process in Sphceroplea is suggestive 

 of that in the Fucacece. In the latter, however, we have the addi- 

 tional feature that the female gametes or eggs escape into the water, 

 and copulation takes place outside of the oogonium. Probably no 

 other representative of the algae is so favorable for the observation 

 of the external phenomena of the sexual process than is Fucus. 



The more obvious details of the process have been observed by 

 Thuret, Oltmanns and others, but it is to the recent researches of Far- 

 mer and Williams ('96, '98) that we are indebted for a thorough 

 and comprehensive account of the phenomena to be observed in the 

 living material. The work of these authors supplements also the 

 observations of Strasburger ('97) on the development of the gametes 

 and on the behavior of the sperm-nucleus after it enters the egg. 



The type of division of the cell and nucleus in the development of 

 the gametes in this group of plants has been fully treated in the intro- 

 ductory chapter, and the escape of the egg-cells from the oogonium is 

 too well known to bear repetition in this place. 1 Since, however, 

 Fucus has figured prominently in recent and much discussed theories 

 bearing upon the significance of the number of the chromosomes in 

 sex and heredity, it is probably not out of place here to state that, in 

 the first nuclear division in the oogonium, the reduced number of 

 chromosomes appears, and that both the nucleus of the egg and the 

 spermatozoid contain this number. 



In order to observe the behavior of the sexual cells while alive, and 

 to obtain suitable material for the indirect method of study, Farmer 

 and Williams state : 



Male and female plants were kept in separate dishes, and were covered to 

 prevent drying up. ... On the appearance of the extruded products, the 

 female receptacles were placed in sea-water, and after the complete liberation 

 of the oospheres a few male branches with ripe antherozoids were first placed 



1 On the method of the liberation of the sexual cells, see Farmer and Williams, '98, p 629. 



