2mn 

 I I 



zeolite fibres. Both these substances have a refractive index 

 less than 151. The isotropic material shows irregular cracks, 

 and has the properties of opal. Its reflective index is con- 

 siderably below that of the brown glass. These zeolitic 

 patches are developed quite irregularly between the con- 

 stituents of the ground-mass. 



In some cases the vesicles were formed prior to the final 

 consolidation of the rock as they are surrounded, externally, 

 by the ground-mass felspar laths arranged tangentially to 

 the spherical surface of the vesicle. 



This rock is thus distinctly related to the tholeiite type 

 of basalt, but shows some affinities with the innimmorites, 

 in the presence of a uniaxial augite, and the presence of opal 

 in the vesicle substances indicates an acidity more comparable 

 with the latter. The rock bears no relation petrographically 

 with the Palaeozoic dyke rocks of the Blinman and Victor 

 Harbour districts, and there can be no question of its relation 

 to the Tertiary igneous rocks of the Kingscote area. The 

 basalts of Kingscote have been shown by Stanley (Trans. Roy. 

 Soc.'S. Austr., vol. xxxiv., 1910, pp. 69-74) to be enstatite 

 types of comparative high acidity (53% Si0 2 ). By the pre- 

 sence of the enstatite molecule in the monoclinic pyroxene, 

 this tholeiitic basalt is petrographically linked with the 

 enstatite basalts, and it is probable that they represent terms 

 in a common differentiation series. 



C. E. Tilley. 



Evening Meeting, April 14, 1921. 



Loranthus and Its Hosts. 



Dr. J. B. Cleland exhibited specimens of Loranthus 

 showing the remarkable resemblance each bore to the general 

 appearance of the particular hosts. Thus Loranthus exocarpi 

 on the cultivated olive (and oleander) ; L. miraculosiis on 

 Myoporum plat y car p u m ; Lj. sp. near L. gihberulus on 

 Casuarina and L. hnophyUus on Acacia Burkitti, were in some 

 instances almost indistinguishable when growing from the 

 trees or bushes on which they were parasitic. Why this 

 resemblance ? 



(1) The suggestion that the resemblance is a protective 

 device of advantage to the mistletoe can at once be dismissed. 

 The mistletoe, being spread by birds feeding on its fruits, is 

 more likely to court observation than otherwise. 



(2) May the resemblance be due to some hormone devel- 

 oped in the host reaching the parasite by means of the sap 

 and thus modifying and controlling the development of the 



