No. 493] THE PHEXOGAMOUS PAIL I SI TES 



19 



condition of complete parasitic phenogams, but those 

 which are only partially normal supplement their honest 

 gains by theft. They are all robbers, and obtain new 

 organic substances from their hosts by methods which 

 resemble grafting, budding and leeching, respectively. 

 In the first two cases mentioned the embryo of the para- 

 site is thrust into the living tissue of the host from which 

 the resulting parasitic plant draws its nourishment, much 

 as do the bud and scion in cases of budding and grafting. 

 In the other case special organs, namely, haustoria, are 

 developed as instruments of robbery. These organs serve 

 to draw new organic substance in liquid form from nor- 

 mal plants, and they are as indispensable to the parasite 

 which possesses them as are roots to normal plants. 

 They are produced as small outgrowths from different 

 parts of different parasitic species, sometimes upon the 

 roots and sometimes upon the stem and branches. They 

 are of wart-like, discoid, globular, or more or less irreuu- 

 lar form, and are sometimes single and symmetrical, but 

 oftener in groups or clusters and shapeless masses. 

 When single they are sometimes sessile and sometimes 

 terminal on slender pedicels. They attach themselves by 

 their free surface to the host, and so burrow into its sub- 

 cortical and subcortical tissues that the growing cells of 

 both i .hints are intimately commingled. Acting like 

 suckers, they withdraw in liquid form the new organic 

 substance which the host had prepared for its own use. 

 much as a leech extracts blood from its victim. The 

 haustoria of parasites are comparable with roots of nor- 

 mal plants because, like roots, thev are the instruments 

 by means of which the plants obtain necessarv supplies, 

 but true haustoria are not roots nor morphological repre- 

 sentatives of them. 

 The foregoing remarks apply mainly to the general 



phytes, symbionts and' normal plants. Vhe special char- 

 acteristics of the parasites are grouped and briefly sum- 

 marized in the following synopsis. In remarks which 

 follow each synoptical statement some of the more con- 



