BY J. MCLUCKIE. 579 



of contact would eventuate in a flow of dissolved foods and, since the parasitic 

 parenchyma cells, with their thin walls, large nuclei and abundant cell-sap when 

 compaxed with the phloem elements of the host, represent a more efficient osmotic 

 system, the natural tendency would be for diifusible foods to enter the haus- 

 torium. 



The presence of laticiferous-like tubes in the liaustorium is an important fact 

 from the physiological point of \dew. These elements have no connection with 

 the phloem of the host; they pass down the axis of the haustorium, spreading 

 out in different directions towards the tip of the haustorium. They frequently 

 occur in groups, close together, and stand out in distinct contrast to the or- 

 dinary parenchyma of the haustorium. They are unthickened and in numerous 

 eases are connected to the traeheids of the haustorium. Since they are not in 

 contact with the host's phloem elements, I conclude that they represent food- 

 conducting structures between the haustorium and the aerial parts of the para- 

 site. The occurrence and distribution of these structures is further evidence of 

 the improbability of Notothixos normally tapping the food reserves of the host. 

 The presence of considerable quantities of reserve food in the laticiferous-like 

 elements and in the parenchyma of the haustorium suggests that the haustorium, 

 during the inactive vegetative periods of the parasite, functions as a storage 

 tissue. While the evidence available supjaorts the view that chlorophyll-bearing 

 parasites such as Notothixos are water parasites under normal conditions, it is 

 quite possible that circumstances may occur from time to time, which may dis- 

 turb the normal physiological balance between host and parasite, so that the 

 parasite may withdraw food from the host-tissues. 



Summary. 



1. Notothixos incanus var. submireui: is commonly parasitic upon species of 

 Loranthus, but may occur upon species of Eucalyptus, Fhyllanthus, and 

 Casuarina. 



2. The fruit is small, semi-succulent, and covered with the golden hairs charac- 

 teristic of the species. 



3. Dissemination occurs during moist weather when transpiration from tlie 

 plant is reduced and the moisture content of the fruits is increased. 



4. The seed is covered with a gelatinous coat, the cells of which are so arranged 

 that extrusion. takes place from the base of the fruit after it has been shed 

 from the plant. The walls of the gelatinous cells consist of two layers, 

 namely, an outer mucilaginous and an inner, spirally-coiled, cellulose layer. 



5. The seeds germinate on living or dead twigs and leaves, on the ground or 

 on fences. The gelatiaous seed-coat provides the embryo with water until 

 it has penetrated to the xylem of the host. 



6. The root has no root-cap; it is not geotropically sensitive, but is negatively 

 phototropic and frequently executes considerable curvatures to bring its 

 apex into the favourable light relation. 



7. A holdfast develops from the root-apex when it presses against a resistant 

 body; and from the centre of this holdfast the haustorial tissue grows into 

 the host's tissues. 



8. The haustorium penetrates the host by pressure and chemical solution; its 

 peripheral layer is slightly papillate. 



9. A cambium is developed in the haustorium, partially replacing the cambial 

 ring of the stem; from this cambium secondary tissues are developed in a 



* radial manner. 



