SEAWEEDS AND THE WATER-FLORA. 1 83 



cells surrounding a central chain, and the stem has 

 branches and special attaching cells. In the highest 

 types, such as Fucus and Laminaria, there are bodies 

 of cells. Those cells which form the skin are small 

 and full of chlorophyll grains, whilst the cells become 

 larger towards the inside of the frond, those in the 

 centre being a loose entangled network of long 

 colourless cells, probably used to conduct the food 

 material. There is, therefore, clearly a definite division 

 of labour amongst the cells. Not only so, but in Fucus, 

 Laminaria, and Rhodophyllum there are rootlike, stemlike, 

 and leaflike organs. In the latter case, the leaves have 

 an extraordinary resemblance to those of the dock. 



Chara is even more remarkable, for here the upright 

 stem with branches, leaves and apparent flowers, has a 

 very distinct analogy to that of the higher plants. 



It is this variety of shape and architectural plan, and 

 the extraordinary differences of the reproductive organs, 

 that give so much botanical importance to the whole 

 group. They are certainly the lowest and least 

 specialised of plants, and show attempts at develop- 

 ment in many different directions, whilst the lines of 

 ascent are more or less definitely determined in all 

 the higher groups. 



As regards the methods of reproduction, it is un- 

 necessary to give many details, as this is very fully given 

 in many English text-books. There are four distinct 

 kinds of reproductive bodies and two methods of 

 reproduction — Nonsexual and Sexual. Nonsexual repro- 

 duction of the simplest conceivable type occurs in 

 Pleurococcus and Sphaerella, where the single cell divides 

 into two new ones, which are in all respects similar 

 to their parent. Obviously this is not distinguishable 

 from ordinary growth. In the higher Algae, such as 



