VA UCHERIA. 



145 



fertilized egg (sometimes called here the oospore). It is freed 

 from the oogonium by the disintegration of the latter, sinks into 



Fig. 142. 



Fertilization in vaucheria. w, male nucleus ; fn, female nucleus. Male nucleus entering 

 the egg and approaching the female nucleus. (After Oltmans.) 



the mud, and remains here until the following autumn or spring, 

 when it grows directly into a new plant. 



305. Fertilization. Fertilization is accomplished by the 

 spermatozoids swimming in at the open end of the oogonium, 



Fig. 143. 



Fertilization of vaucheria. fn, female nucleus; tun, male nucleus. The different figures 

 show various stages in the fusion of the nuclei. 



when one of them makes its way down into the egg and fuses 

 with the nucleus of the egg. 



306. The twin vaucheria (V. geminata). Another species of vaucheria 

 \s the twin vaucheria. This is also a common one, and may be used for 

 >tudy instead of the sessile vaucheria if the latter cannot be obtained. The 

 sexual organs are borne at the end of a club-shaped branch. There are 

 usually two oogonia, and one antheridium between them which terminates 

 the branch. In a closely related species, instead of the two oogonia there is 

 a whorl of them with the antheridium in the center. 



307. Vaucheria compared with spirogyra. In vaucheria we have a plant 

 r hich is very interesting to compare with spirogyra in several respects. 



