CHAPTER XXVI 



PARASITES, ENSLAVED PLANTS, MESSMATES, 

 CARNIVOROUS PLANTS 



404. Parasites. A little was said in Chapter IV about 

 parasitic plants, and the life history of one of them, the 

 dodder, was briefly outlined ; another, the wheat rust, was 

 discussed in Sects. 310-313. A parasitic plant is one 

 which draws its supply of food partially or wholly from 

 another living plant or animal known as the host. Some 

 parasites are seed-plants, but a far greater number of 

 species are spore-plants. 



405. Half -Parasitic Seed-Plants. Half-parasites or par- 

 tial parasites are those which take a portion of their food (or 

 of raw materials to make food) from their host and manu- 

 facture the rest for themselves. Usually they take mainly 

 the newly absorbed soil-water from the host and do their 

 own starch-making by combining the carbonic acid gas, 

 which they absorb through their leaves, with the water 

 stolen by the parasitic roots or haustoria imbedded in the 

 wood of the host. Evidently the needed water may just 

 as well be taken from the underground parts of the host 

 as from the upper portions, and accordingly many half- 

 parasites are parasitic on roots. This is the case with 

 many of the beautiful false foxgloves (G-erardia), with the 

 painted-cup (Castillea), and some species of bastard toad- 

 flax ( Oomandra) ; see Flora. Usually these root-parasites 

 are not recognized by non-botanical people as parasites at 



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