Introduction 



In the families of flowering plants which show saprophytism 

 and parasitism there occur usually green purely autophytic 

 plants with typical green leaves and numerous flowers; plants 

 that are purely saprophytic or parasitic, with colorless scales 

 and a reduced number of flowers; and all gradations between. 

 In a comparative study of such typical families showing sapro- 

 phytism, i.e., the Burmanniaceae, Orchidaceae, Gentianaceae, 

 and Ericaceae, and those showing parasitism, the Loranthaceae, 

 Santalaceae, Balanophoraceae, Rafflesiaceae, Lauraceae, Con- 

 volvulaceae, and Scrophulariaceae, one notices a common ten- 

 dency in the saprophytic or parasitic members toward condensa- 

 tion and simplification as the saprophytism or parasitism be- 

 comes more pronounced. To illustrate from the parasitic group, 

 in the Loranthaceae the genera Nuytsia and Gaiadendron are 

 upright independent trees; the genus Loranthus consists of 

 upright shrubs with large leaves and numerous flowers as L. 

 Baroni Baker and L. pulcher D.C., to those with small leaves 

 and solitary flowers as L. microcuspis Baker and L. stocksii 

 Hook.; Viscum consists mainly of species of condensed habit, 

 small leaves often reduced to scales, and small green unattractive 

 flowers and more or less simplified embryos; finally Arceutho- 

 bium consists of reduced almost leafless parasites becoming 

 slightly yellowish in color with small solitary flowers. In this 

 family, however, the plants still contain chlorophyll. In the 

 Convolvulaceae the parasitism has become so great in the 

 genus Cuscuta that it has completely lost all traces of chloro- 

 phyll, except in the stems of C. reflexa, Roxb. (Hooker in Bot. 

 Mag. t. 6566). From this species we have gradations to others 

 with thick yellow stems like C. exaltata, Engelm.; others with 

 slender yellowish or red stems as C. epilinum Weihe and C. 

 epithymum Murr, pale yellow in C. arvensis Beyrich, and whitish 

 or pale yellow in C. cephalanthi Engelm., and finally to white in 

 C. epithymum var. alba. The leaves are in all cases reduced 

 to microscopic scales; the flowers are small but clustered to- 

 gether; the first or central flowers are five-parted, the lateral 

 ones often four-parted (15), and the embryo is so reduced that 

 it shows no trace of cotyledons. 



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