294 



PHILOSOPHICAL NOTES ON 



Fig. I25(f. Young ^porange isolated from female conceptacle of the same 

 Fucus, with harreu hairs : (6) proba])ly atrophied antheridia. Enlarged. 



l)lacenta of the .sorus. They woukl therefore come under the 

 definition of hairs. 



The sorus-like tufts of alga^ liave no indusium. This appears 

 to be a covering originating in the needs of ferns, connected with 

 atmospheric changes. It may be made up of radiating hairs fused 

 into an umbrelhi-sliaped body, much like the radiated hairs of 

 Fdeagnus. 



Hairs may be remnants not only of reproductive organs proper, 

 but they may be atrophied teeth or lobes of leaves ; they may be 

 atrophied leaves, or bracts ; in short, any part which is inter- 

 changeable with a }>ranch, such as an ovule or other homologous 

 part. 



The development of hairs into bud-scales and leaves would be 

 aualagous to the development of the down of young birds into their 

 adult feathers. 



The involucral hairs of the sorus of Woodsia hyperborea would 

 stand for bracts (pi. 7, " Hooker's Brit. Ferns "). So would those of 

 the algu Helminthora divaricata which surround the cystocarp 

 (Thuret, pi. 32). 



