94 



PLANTS 



2 1 6. Symbionts are organisms which are associated with 

 other plants or animals for the advantage of one or both, but 

 without serious detriment to either. Some forms are found 

 normally only under such relationship. Lichens are a symbiotic 

 combination of a fungus and an alga. A relation of this kind 

 also exists between certain Spermatophytes and some of the 



Fig. 49. — The sun-dew, Drosera. One leaf is shown, with the glandular hairs 



by which small insects are caught. X5/3. 



lower fungi. The mycorhiza, for example, consist of a filamen- 

 tous fungus attached to the roots of seed plants, for which they 

 seem to serve to some extent the office of absorption, and prob- 

 ably receive some compensation in return. 



217. The most important of this class of plant relationship 



