430 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY 



I.— INTRODUCTION. 



The Rhodophyceae are a very distinctive class in the 

 Euphyceae or Algae, which form a sub-division of the 

 Thallophyta. They are separated from the other classes 

 of the Euphyceae by their reddish or violet colonr. This 

 colour is produced by the green chlorophyll being obscured 

 by a red colouring matter, called Phyccerythrin. The 

 Rhodophyceae embrace two sub-classes, namely, the 

 Bangiales and the Floridee. The representatives of the 

 former have very simple and undifferentiated filamentous 

 or membranous multicellular bodies. The sexual organs 

 are extremely simple. The Florideae have multicellular 

 bodies, consisting usually of much-branched rows of cells, 

 which often form plants of good size and firm structure. 



To the sub-class Florideae belongs the subject of this 

 memoir, Chondrus crisjnis, the Irish Moss. With the 

 exception of nine genera, five of which are confined to 

 freshwater, the Floridese are exclusively marine plants. 



The arrangement of the natural orders of the Florideae 

 into series is dependent on the various methods by which 

 the fruit develops after the fertilisation of the female 

 organ. It is unnecessary to refer to the subject in detail 

 here. It must suffice to say that the natural orders are 

 arranged in four series, namely, the Nemalionales, the 

 Gigartinales, the Rhodymeniales and the Cryptonemiales. 



The natural order to which Chondrus belongs is that 

 of the Gigartinaceae, one of the Gigartinales. The only 

 other order of this series, the Acrotylaceae, differs from 

 the Gigartinaceae in the arrangement of the asexual spores 

 in their mothercell. The tetraspores of the latter are 

 formed by cruciate, those of the former by zonate, 

 division. 



