Ill THE COLOURS AND PIGMENTS OF PLANTS 59 



of the Protozoa, there is a constant oscillation between 

 red and green as a ground colour. It seems most 

 probable that this, as in higher plants, is due to 

 a destruction of the chlorophyll green and a conse- 

 quent predominance of an associated lipochrome. In 

 Algae it occurs nowhere in such an instructive way 

 as in the brittle -worts Chara and Nitella. Here 

 virtually the whole plant is coloured green by chloro- 

 phyll, but the reproductive organs, and especially the 

 antheridia, as they ripen become a bright red, the 

 colour being due to the red chromatophores which 

 replace the chlorophyll corpuscles. The whole 

 process is exactly analogous to that which occurs 

 during the ripening of red fruits like the rose-hip. 

 Quite similar is the process which occurs during 

 the maturation of the antheridia of brown seaweeds 

 like Fucus. Here the plant owes its colour to a 

 combination of chlorophyll green, a brown pigment, 

 and a lipochrome. In the oospheres all these three 

 are retained, but in the antherozooids the brown 

 and the green disappear, and the orange-coloured 

 lipochrome remains in the chromatophores and gives 

 rise to the orange coloration. The retention of the 

 chlorophyll in the female elements and its disappear- 

 ance from the male many would regard as an 

 illustration of the greater vegetativeness of the 

 female. These two examples may suffice to show 

 that the processes which give rise to the colours of 

 Angiosperms have very well-marked analogues among 

 Cryptogams. 



