I 82 PLANT LIFE. 



without the algal threads breaking. The large 

 Laminarias and Alarias cling very firmly to the stones 

 and rocks by their peculiar root-like bases. It is not 

 unusual to find a small piece of rock or stone which, 

 although it has been broken off by the waves and has 

 been washed to and fro in the water, is still attached to 

 a I.aminaria ; and what is even more extraordinary, to 

 find very delicate forms, for instance, a group of diatoms 

 which have been attached by thin almost transparent 

 gelatinous threads to a ship's bottom, and carried with it 

 through storms and at high speeds. Even the slender 

 Polysiphonias, growing on rocks exposed to the full 

 force of the winter storms, are seldom broken off. 

 It seems incredible that so weak an attachment could 

 possibly hold them in position. Of course, as the 

 entire surfaces of all Algae are oily and smooth, 

 through mucilaginous changes of the cellulose, there 

 will be but little friction with the water, yet this is 

 by no means a full explanation. 



It is, of course, quite impossible to describe the vast 

 group of Algae. Reference must be made to Dr. 

 Murray's work, or to Harvey's Phycologia Britannica. 

 The way in which the simple, solitary cells of such 

 forms as Pleurococcus have become specialised and been 

 made part of a complex solid body, such as Laminaria 

 or Fucus, can be understood from examining a series 

 of different species. In Spirogyra the cells form a row 

 or filament attached by a clasping cell at the base. 

 Then in Enteromorpha, the cells are combined into a 

 single layer or plane surface, which is sometimes 

 arranged in a cylinder. In such a form as Cladophora 

 or Ectocarpus, the rows of single cells are combined into 

 a sort of branching shrub. In Polysiplionia, the trans- 

 verse section of the stem is made up of a circle of 



