324 PROCEEDINGS OF SECTION D. 



or horizontally spreading branch of the parasite would die, and, so an^ 

 means by which the growing point can turn and retrace its steps, as 

 it were, to the old pasture, is a distinct advantage in the struggle to 

 survive. The branch, while nutating, and finding no foreign body, 

 then increases the angle of divergence from the axis of nutation and 

 continues to increase it until it exceeds 90 degrees, when the branch 

 comes into contact with itself. The loop thus formed is necessarily 

 a small one, of a few centimetres only. There it takes hold and twines 

 along itself in a direction opposite to that of its eorlier growth, as a 

 means to an end, and so retains an area of food supjily probably not 

 exhausted, but, in any case, by this device, to strike out and seek a 

 fresh branch or twig of the host, and, perhaps, eventually an entirely 

 new host in an hitherto unexplored direction. In this phenomenon 

 we have, resulting from the trial and error method, something indi- 

 cative of memory in the plasma of the parasite. It is of such frequent 

 occurrence as to be more than mere accident, and, further, this evidence 

 of a plant having recourse to an abnormal habit, in order to regain union 

 with a host, seems to be a powerful addition to facts already in 

 favour of the theory that the haustoria themselves are " new forma- 

 tions " produced for a special purpose. 



JReferbnces to Litekaturb Noted in Text. 



1. Brown, R. Prodr. Flor. Nov. Holl. ; I. ; 1810 ; p. 404. 



2. Goebel, K. " Organography of Plants." 



3. Pfefier, W. " Physiology of Plants " '(Trans. Ewart), 1900-6. 



4. Ewart. A. J. (and Tovey, J.). " Weeds, Poison Plants, and 

 Nat. Ahens of Victoria, 1909." 



5. Sachs, J. Lectures on the Physiology of Plants (Trans. Ward), 

 1897. 



Note. — The identification of the species Cassytha melantha. 

 Eucalyptus fruticetorum, and E. viridis R.T.B., have been confirmed 

 on reference to the National Herbarium, Melbourne. 



EXPLANATION OF PLATE IX. 



Fig. 1. Heterodendron oleifolium, destroyed and hidden by Cassytha 

 melantha, "which is extending to a new host of the same species 

 (in the background). Loc. North-West Victoria (" Mallee"). 

 (Photo. D. Crosbie.) 



Fig. 2. Cassytha melantha, fruiting, on Eucalyptus fruticetorum and 

 reaching for a new host on the left. Some twigs after futile 

 nutation are returning by means of other twigs to the mala 

 body. Loc. Huntly State Forest. (Photo. A. D. Hardy.) 



