5io May brook.— On the Haustoria of 
only of the haustoria, but also of the roots, the persistence of the proto- 
plasmic contents is a unique adaptation to the absence of phloem, the xylem 
elements being thereby enabled to conduct both organic and inorganic food 
material. 
Summary and Conclusion. 
1. Pedicularis vulgaris is a root parasite capable of attacking both the 
roots of other plants and of itself. 
2. Haustoria of Pedicularis vulgaris were examined in detail and their 
anatomical structure has been described. The structure was found to be 
identical both in the case of attack of a foreign root and of itself. In this 
respect Pedicidaris differs from Olax> which Barber has shown to vary in 
structure in the case of self-attack. 
3. The haustoria were found to possess phloeotracheides, which, however, 
differed from those described by Benson for Exocarpus in being nucleated. 
4. The xylem tracheides of the roots and of the piliferous layer of the 
haustoria were found to possess abundant protoplasmic contents. 
5. Phloem was found to be absent from both the roots and the haustoria 
of Pedicidaris vulgaris. This phenomenon was concluded to be correlated 
with the retention by the xylem tracheides of their protoplasmic contents. 
In the roots the place of the phloem is taken by elongated parenchymatous 
cells. 
6. Pedicidaris vulgaris being a root parasite is characterized by less 
highly differentiated haustoria than is found in stem parasites. The con- 
ducting cells are not specialized for the conduction of either organic or 
inorganic materials, but are capable of conducting them both indis- 
criminately. 
The above piece of work was carried out in the Westfield College 
Laboratory during my tenure of research scholarships awarded by the 
Westfield College Council and by the London County Council. I wish to 
acknowledge the helpful advice and guidance I have received from 
Dr. de Fraine in this connexion. 
Bibliography. 
Barber, C. A. : Studies in Root Parasitism— The Haustoria of Santalum album . Mem. Dep. Ag. 
Ind., Bot. Ser., vol. i, 1906-7. 
: Studies in Root Parasitism— The Haustoria of Olax scandens . Mem. Dep. Ag. Ind., 
Bot. Ser., vol. ii, 1907. 
