THE ALG.E 175 



web, and are often troublesome weeds, especially to Fern 

 cultivators. Their threads are rather coarse, darkish- 

 green, and branched. When submerged, they often form 

 dense masses of large size, becoming conspicuous objects 

 in the water. 



1. STRUCTUKE 



In the vegetative condition a Vaucheria consists of a 

 cylindrical green filament, repeatedly branched at irregular 

 intervals, and attached by a colourless branched root or 

 rhizoid (see Fig. 75, B). The contents are uniform 

 throughout the green part of the plant. The filament is 

 bounded externally by a cellulose membrane, but internally 

 there is nowhere the least trace of cell-walls, so long as 

 the plant remains in its normal vegetative condition ; the 

 cell-contents are uninterrupted throughout its entire 

 length (which may amount to many inches), and extend 

 without a break into the branches. 



The protoplasm forms a thick layer lining the external 

 wall, and contains an immense number of roundish 

 chlorophyll-granules, the abundance of which accounts for 

 the deep-green colour of the threads. Imbedded in the 

 protoplasm, just inside the layer of chlorophyll-granules, 

 there are innumerable minute nuclei, which multiply by 

 division as the plant grows. This feature is very character- 

 istic of the Siphoneae and some allied Algae, which always 

 have very numerous nuclei scattered in their protoplasm. 

 We see, then, that Vaucheria possesses the essentials of 

 histological structure protoplasm and nuclei though 

 not partitioned into distinct cells. The growth of the 

 stem and its branches is apical ; at the extreme growing 

 end of each filament the protoplasm is colourless and 

 transparent. Vaucheria does not form starch ; the pro- 



