54 Ellen Marion Delj 



lettuce) are frequently found growing on larger Algae, and the 

 delicate threads which are woven together to form the little attach- 

 ing- disk of this plant, are able to pierce the cells of its host and 

 probably to absorb food from it, although this last point is a very 

 difficult one to determine experimentally. In many cases no 

 such penetration of the host plant can be detected, and we must 

 suppose that any advantage derived from the epiphytic habits of 

 these plants depends upon the protection from exposure, or possibly 

 in the more crowded habitats, from a greater access to light. 



On any rocky shore at low tide, it is at once easy to distinguish 

 three varying types amongst seaweeds, green, brown, and red, the 

 last varying from rose red in the more sheltered habitats, to deep 

 brown or brownish red in the more exposed positions. On these 

 shores the dark brown-red forms are very characteristic. These 

 colours cannot always be observed in the drift weed cast up after 

 rough weather, as the fronds are apt to become bleached in the 

 sun, as they die. 



These pigments have a real significance in the life of the plant, 

 and play their part in determining the position in which a par- 

 ticular kind may be found. All these pigments undergo decom- 

 position in bright daj'light, but during life they are also being con- 

 stantly re-formed. On the whole it seems probable that the red 

 and brown pigments are more sensitive to light than the green 

 v/hich often accompany them; at any rate, the more 

 delicate pink seaweeds are always found in deep water 

 or else in deep shade; whilst when any red or brown Alga under- 

 goes bleaching in sunlight, the red or brown fades first and finally 

 thc:: undertying green colour is also destroyed. This may some- 

 times be seen in pools at low water during spring tides, when ex 

 posed tips of red seaweeds (such as Hypnea spicifera or Suhria 

 prhiioides at Kalk Bay for example) may be seen, bright green in 

 colour, projecting from the water whilst the rest of the shoots are 

 submerged and are red or purplish red in colour. 



When the pigments are extracted from the plant and examined 

 spectroscopically it is found that whereas the green pigment chloro- 

 phyll absorbs light principally from the red end of the spectrum. 



