52 PLANT LIFE OF ALABAMA. 



PARASITIC PLANT ASSOCIATIONS. 



True parasites are also destitute of chlorophyll, and leafless, but 

 they take their nourishment from the living tissues of their host, sub-* 

 sisting entirely on its elaborated food materials. Three species of 

 this class of parasites which foist themselves upon the roots of their 

 hosts (root parasites) occur in the Carolinian zone of Alabama, and 

 are also frequently found in other parts of temperate North America, 

 all belonging to the family of broom rapes (Orobanchaceae), namely: 



Conopholis americana, Thalesia uniflora. 



Leptamnium (Epiphegus) mrginianum. 



Of the parasites which fasten themselves upon the stems of their 

 host, 6 are found in Alabama, all belonging to the dodders or love vines 

 (Cuscuta). These plants at the start root in the ground, but upon 

 springing up, when they meet a plant suitable for a host they wind 

 themselves around its stem and at places of close contact send haus- 

 toria through its bark to the wood, and, the cells of the two uniting, 

 the parasite draws its food from the plant attacked. Thus firmly 

 established, the part of the stem of the parasite connecting it with the 

 ground dies, and it depends henceforth entirely for its nourishment 

 on its host. The chlorophyll-bearing shrubby parasites of trees are 

 represented by a single species, the American mistletoe (Pliorobdendron 

 flavescens). 



The so-called heiniparasites green herbs which fasten themselves 

 by their lateral rootlets upon the roots of their host are only partly 

 dependent upon assimilated food material. These half -parasites belong 

 mostly to the figwort family, examples being Canadian louse wort 

 (Pedicularis canadensis), painted cup (Castilleja canadensis), and sev- 

 eral Gerardias. The number of plants subsisting in this way has not 

 been ascertained, but outside of the Scrophulariaceae, Comandra and 

 Darbya are also supposed to be hemi-parasites. 



INSECTIVOROUS PLANTS. 



A class of these plants inhabit the bogs of peat mosses and the damp 

 flat open pine barrens of the Coast plain, consisting of sarracenias 

 (Sarracenia), sundews (Drosera), butterworts (Pinguicula) ; and others, 

 viz, the bladderworts (Utricularia), inhabit stagnant or still-flowing 

 waters of shallow pools, ponds, lakes, and streams, floating upon the 

 surface of the water or immersed. It is evident that by the faculty of 

 appropriating animal substances for their nourishment, nature has 

 provided these plants with an additional supply of nitrogenous food 

 which the sterile soil, extremely deficient in the elements required for 

 plant nutrition, does not contain. In order that they may get hold of 

 the animals serving them for food they are endowed with peculiar 

 appliances of a highly specialized character, as, for example, the 



