ABSORBING SYSTEM OF ALGAE AND FUNGI. 259 



IV. THE ABSORBING SYSTEM AMONG THE 

 THALLOPHYTA. 



Most Algae absorb food-materials through the whole of their outer 

 surface ; these plants, accordingly, have in general no need of a special 

 absorbing system. The multifarious root-like structures which never- 

 theless occur in this group serve almost without exception only as 

 organs of attachment. There are a few species of Algae, such as 

 Botrydium granulatum, which lead a terrestrial existence; the richly 

 branched rhizoids by which Botrydium is fastened to the soil are 

 no doubt utilised for absorption as well as for fixation. Further 



Pig. 105. 



Haustoria of parasitic Fungi (Peronosporeae). A. Cystopus candidusin the pith of 

 Lepidium sativum ; m, intercellular hypha with knob-shaped haustoria. B. Perono- 

 spora calotheca in the pith of Asperula odorata; in, intercellular hypha with much- 

 branched filiform haustoria ; z, z, host-cells. 



investigation is needed in order to determine how far the various 

 trichomes which occur in the higher groups of Algae, such as the 

 Florideae and Phaeophyceae, are employed for the absorption of 

 nutrient materials. Ileinke and Wille m are probably right in 

 supposing that the tufted hairs of the Laminariaceae and Fucaceae, 

 which occur on the surface of the thallus in the former group, but are 

 sunk in the so-called sterile conceptacles [cryptostomata] in the latter, 

 are organs of absorption comparable to root-hairs. In support of this 

 contention Wille lays stress on the ease with which many coloured 

 solutions pass into these trichomes, and from them into the conducting 

 tissues of the thallus. 



Among the Fungi 135 the great importance of the absorptive function 

 exert a far-reaching influence upon the form and structure of the 



