Lecture XV III. 



139 



neck is occupied by a single column of elongated cells when 

 these cells disintegrate they leave a canal leading down the neck 

 to the ovum. 



The sperm-cells, which by this time have disentangled them- 

 selves from the debris of the mass of sperm-mother-cells expelled 

 from the antheridium, are attracted to the necks of the mature 

 archegonia. A single sperm passes through the fluid remains of 

 the neck-canal-cells and makes its way to and fuses with the ovum. 

 The final maturing stages of the archegonia and antheridia can 

 only take place in presence of water and this at the same time 

 supplies a water-way for the transit of the sperms from the male 

 to the female branch. The guidance of the sperms in this passage 

 seems to be due to the formation of a chemo- 

 tactic substance emitted by the archegonia, 

 developed possibly from the disintegrating neck- 

 canal-cells. The nature of this substance can 

 only be inferred from the fact that it has been 

 found, possible to divert sperms from their 

 natural goal by introducing a source of sucrose 

 into the liquid submerging the sexual shoots. 

 Thus it has been observed that sperms will 

 turn aside from archegonia and travel towards, 

 and finally enter capillary glass tubes contain- 

 ing a solution of that sugar. The extreme 

 sensitiveness of the sperms to such influences 

 may be judged by the fact that a solution of 

 o'ooi per cent, exercises an attraction for them. 

 These chemotactic responses are particularly 

 interesting as they afford a chemical and me- 

 chanical basis for a phenomenon which might 

 otherwise be attributed to spontaneity or pur- 

 poseful volition. 



The fertilised ovum, or oosperm, in the archegonium divides 

 into an upper and a lower hemispherical cell. They each by 

 oblique divisions give rise to an apical pyramidal cell. The 

 lower one produces a small mass of tissue the foot which 

 presses into the bottom of the archegonium, and makes firm con- 

 nection with it ; the upper forms a cylindrical mass which grows 

 much more vigorously and pushes the upper part of the arche- 

 gonium before it. At first the growth and stretching of the 

 archegonium keeps pace with the elongation of the embryo it 

 contains, but later the archegonium is torn by the embryo's con- 

 tinued growth, and the upper part is separated as a cap the 



FIG. 28. Fnnaria 

 hygrometrica, 

 showing female 

 (/) and male (m) 

 branches of 

 gametophyte, x 

 about 10. (After 

 Collins.) 



