Notes on Parasitic Seed Plants with Reference to Cuscuta

The parasitic habit has been developed in relatively few of the higher land plants. No Bryophytes or Pteridophytes are known to be parasitic, and but comparatively few Spermatophytes obtain their food in this manner. No parasites are known in the Gymnosperms. From a taxonomic standpoint the parasitic habit in seed plants is highly restricted. Among the 150,000 Angiosperms approximately 2,000 species are parasitic. This figure includes both partial and obligate parasites. Of this number less than 700 are totally dependent upon a host; the remaining species being able to manufacture at least a part of their food supply. The majority of parasitic Angiosperms occur in tropical and sub-tropical regions