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. STRUCTURE 



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, as 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 non-cellular Algse and some allied forms, 

 which always have numerous nuclei scattered in their 

 protoplasm. We see, then, that Vaucheria possesses the 

 essentials of cell - structure protoplasm and nuclei 

 though not partitioned into distinct cells. The growth of 

 the stem and its branches is apical ; at the extreme grow- 

 ing end of each filament the protoplasm is colourless and 

 transparent. Vaucheria does not form starch ; the pro- 



