4/2 



Mr. H. C. Sorby on 



[June 19, 



my analyses are calculated out, so as to compare the different specimens, 

 on the supposition that the amount of orange xanthophyll is constant. I 

 examined five examples of the plant, growing in very different situa- 

 tions, viz. : — ■ 



I. Where very damp and shady, so that no fructification was developed. 



II. Where open to the sun, but slightly shaded by the grass amongst 

 which it grew, and having fructification developed to great perfection, 

 which of course was separated. 



III. Kather more exposed to the sun, with no fructification. 



IV. Still more exposed to the sun. 



V. Very much exposed to the sun, growing on a bare rock, and being 

 of much browner colour than I., II., and III., which were of a most 

 decided green. 





Blue 

 chlorophyll. 



Chlorofucine. 



Phyco- 

 xanthine. 



Orange 

 xanthophyll. 



Lichno- 

 xanthines. 



I. 



61 



100 



65 



100 



40 



II. 



100 



99 



100 



100 



95 



III. 



86 



73 



79 



100 



100 



IV. 



43 



54 



76 



100 ' 



71 



V. 



32 



51 



64 



100 



67 



On comparing these together it will be seen that the specimen with 

 such abundant fructification (II.) contained the maximum, or nearly the 

 maximum, quantity of all the different colouring-matters, as though the 

 amount of light were just that best suited for its growth. The specimen 

 in extreme shade (I.) shows a remarkable falling off in some of the con- 

 stituents, as if the plant were in a sickly state ; and the small amount of 

 the lichnoxanthines is particularly interesting, because they are the special 

 colouring-matters of the fructification, which in this specimen was not 

 developed, perhaps for that very reason. The difference in the pro- 

 portion of the other substances in the specimens more and more ex- 

 posed to the sun (III., IV. & V.) is in strict accordance with the laws already 

 explained, and the reduction in the amount of chlorophyll is most re- 

 markable. The lichnoxanthines, however, do not follow that law, but 

 seem more connected with the presence or absence of fructification. In 

 reference to this question I may mention that, as before named, the 

 antherozoids of Fucus serratus are exclusively, or almost exclusively, 

 coloured by orange xanthophyll, which occurs only in small quantity in 

 the fronds themselves. Taking two portions of the plant, one from the 

 lower part of a frond bearing many well-developed antheridia, and the 

 " other from a similar part of a froud of the same specimen with no • 

 antheridia, I found that the amount of orange xanthophyll was about 

 40 per cent, less in the former, as though this substance had been to a 

 considerable extent drawn off from the frond to supply the antherozoids. 



