CHAPTER X 



DEPENDENT PLANTS 



Some plants, like animals, cannot make their own food, but 

 depend upon other plants for their food supply. 



Parasites and Saprophytes. — A plant which depends 

 upon another living plant is a parasite. Red rust is a para- 

 sitic plant which attacks corn-fields and gives the grain a sickly- 

 yellow look. It may have been living in the seed when it was 

 sown, and only needed moisture which the grain supplied, to 

 grow and send its colourless threads through the straw. When 

 it fruits, short threads break through the surface of the straw or 

 leaves of the grain, and on their tips small spores are borne. 

 Spores formed in the early part of the season are red. Later, 

 black spores are formed. The spores make red or black patches 

 on the plant. When ripe they are blown by the wind on to 

 other plants, where they grow and send small threads down into 

 the grain again. Since they are taking the food, or some part 

 of it, which the grain-plant is making, the heads of grain do 

 not fill out properly. For this reason, farmer's try to get seed 

 from countries where the rust has not injured the grain. 



Dodder {Cuscuta) and Cassytha are parasites which have 

 lost their leaves and most of their chlorophyll. At some season 

 of the year, however, Cassytha stems are quite green. Try to 

 loosen the hold of these plants from the plants around which 

 they are twining and they betray their means of living. They 

 sergi out root-like bodies which penetrate their host (as the 

 plant is called which supplies another with food) and appropriate 

 all the food they require. 



Mistletoe and its relative Loranthiis penetrate their host 

 in a similar manner. They caimot obtain food from the soil 



