BEOWN SEAWEED 83 



degree that they actually produce a shoot, which may 

 break away and become an independent plant. Thus 

 injury stimulates growth, and within reasonable limits 

 Pelvetia is urged to thrive and propagate by " the slings 

 and arrows of outrageous fortune." 



It is in the late summer and autumn that we have 

 the best opportunity for studying sexual reproduction 

 in Pelvetia. Then we notice that some of the branches 

 become enlarged at their ends, the enlarged parts being 

 studded with wart-like protuberances. The hand- 



FlG. 28 — CONCEPTACLE OF PELVETIA CANALICULATA IN MEDIAN SECTION. 



X ABOUT 10. 



o, One of the egg-cells occurring among the barren hairs (paraphyses). 



magnifier helps us to see that at the top of each of these 

 protuberances there is a tiny opening leading into the 

 interior ; indeed, the pore opens into a cavity, called the 

 " conceptacle " (see Fig. 28), where are the organs of 

 reproduction. Both male and female organs are found 

 in the same conceptacle. Large, well-nourished egg-cells 

 are found at the base. The male organs (antheridia) 

 are developed on some branched filaments (see Fig. 29), 

 and both kinds of organs occur among numerous barren 



