ROOTS OF ALGJE AND FUNGI. 



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not divided into cell-chambers; but it has already been pointed out that this simple 

 non-cellular structure nevertheless does not prevent 

 them from exhibiting all the essential physiological 

 properties of a typical root. 



In those Algae the shoots of which are simple 

 segmented filaments, or rows of cells, as in the genera 

 (Edogoiiiu?7i, Cladophora, and others, the root is usually 

 very small in proportion to the green shoot, since this 

 small size, with very simple organisation, suffices to 

 supply an organ of attachment, the mechanical 

 action of which, considering the mode of life of 

 these plants, is very little called into play. In the 

 genus Spirogyra we meet even with the extreme case 

 in this connection, that in the germination of the 

 spore the shoot portion becomes vigorously developed, 

 while the root end is only indicated, as it were, and 

 no longer used even as an organ of attachment ; the 

 simple unbranched filaments of this alga float, in fact, 

 quite free in the water. Nevertheless the ability to 

 form roots is not wanting in Spirogyra; if its long 

 filaments are cut up, and the pieces laid on wet peat, 

 some of their cells put out branched colourless tubes, 

 which behave like roots. In this connection we find 

 similar cases also in highly developed plants ; on the 

 one hand, the rooting of severed portions of shoots in 

 many vascular plants ; on the other hand, the eff'ect 

 which continued contact with a solid body exerts on 

 the development of new roots, as e.g. in Cusaila, and 

 the gemmae of Marchanlia. 



Passing over finally to the Fungi, it has already 

 been mentioned in the first lecture (p. fi), that the mycelium of these resembles 



Fig 23.— Development of zoospores of 

 aidogoniuin (after Pringsheiin X 350). AB 

 zoospores arising from an old filament ; 

 C free zoospore (motile) ; D the same be- 

 ginning to germinate ; E a zoospore formed 

 from the entire contents of a germinated 

 swarm-spore ; root and shoot are to be dis- 

 tinguished in the latter. 



e 



Fig. 24.— Germination of Sftrogyra ju£nlis (after Pringslieim in • Flnra,' no. 30. 1852). / resting zygospore ; // the 

 same beginning to germinate; /// further developed (the zygospore was enclosed in the cell C of a filament on 

 which the conjugating apparatus is still visible) ; e outer cellulose wall of spore ; / yellowish brown membrane ; 



g the third innermost membrane of the spore, which forms the germii 

 the posterior end (d) of wliich grows out as a narrow root process. 



tube 



' w' first septa of a germinal tube. 



typical roots from the physiological point of view ; it has, however, to take up not 

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