224 THE BIOLOGY OF FLOWERING PLANTS 



toe to any morphological category, for the reason that its 

 morphology is very obscure. At first sight it looks Hke 

 an adventitious root system modified in the special circum- 

 stances in which it grows. But neither the suckers nor their 

 branches in the cortex have any root-like characters apart 

 from their absorbing function. Anatomically they are not 

 root-like ; they are produced exogenously, they have no 

 root caps. The actual suckers of the mistletoe, as of the 

 parasites already described and of those about to be con- 

 sidered, are frequently called haustoria, sl term with a very 



Fig. 25. — Mistletoe: i, long section through host and parasite; 

 2, seedling mistletoe at S ; 3, branch of host with bark removed to show 

 course of absorbing system of mistletoe from which adventitious buds 

 arise at X. All nat. size. (After linger.) 



wide and vague application, which is perhaps better left to 

 describe certain definite organs of some parasitic fungi. 

 In the Rhinanthoidese the suckers are, definitely, modified 

 side roots, and this is probably the case in the Santalaceae ; 

 but in Viscum the whole absorptive system may best be 

 regarded as a group of special organs which has arisen in 

 relation to the peculiar circumstances of the plant. 



The mistletoe possesses abundant green foliage and has 

 even chlorophyll in the absorbing system. Its connection 

 with the host is primarily through the wood ; it, too, is a 



