FUCUS. 61 



be seen to approach the oospheres, to apply them- 

 selves closely to their surface, along which they creep : 

 if present in considerable numbers, they give to the 

 oospheres an irregular rotating movement. 



Actual coalescence of the antherozoid with the oosphere is 

 difficult to observe, and it is even doubtful whether it has ever 

 been seen : the appearance of a second nucleus in the oosphere 

 has, however, been described, and its coalescence with the nucleus 

 of the oosphere : it is probable that if an antherozoid, as such, 

 enters the oosphere, its entry is very rapid. 



XII. The most satisfactory way of tracing the deve- 

 lopment subsequently to fertilisation is by artificial 

 cultivation: this has been done by Rostafinsky, 

 so as to prove that the fertilised ovum develops 

 directly into the Fucus plant ; but the cultures, being 

 difficult to carry out, are not fitted for class demonstra- 

 tion. It is thought that the following simple observations 

 will suffice. 



On stones, in districts where Fucus abounds, there 

 may be found in early summer olive-brown velvety 

 patches : on examining these with a lens, small club- 

 shaped bodies may be distinguished, attached by their 

 narrower end to the substratum, and with their 

 broader, free end crowned by a tuft of hairs : these are 

 young plants of Fucus, or of one of the allied genera. 



Having collected such material, and treated it as 

 above directed, tease it out with needles, in glycerine, 

 and examine the plants thus separated under a low 

 power : the following points are the most worthy of 

 note 



1. The nearly spherical form of the very young 



