8 PRESIDENT'S ADDRESS. 



has been devised for measuring the growth of plants, and con- 

 sists of a lever with a long and short arm, the latter being 

 attached to the shoot, whose growth is much magnified by the 

 movement of the end of the long arm. The effect of various 

 treatments of the plant on its growth can in this way be noted. 

 It is generally considered that light is necessary for the 

 development of chlorophyll, the green colouring matter of 

 plants, but an alga (Scenedesmus acutus), which has been culti- 

 vated in the dark for eight years, is as green as others grown in 

 the light, shewing that light is not always necessary. We have 

 been accustomed to look upon the common ragwort (Senecio 

 jacobcea) as a troublesome weed but harmless. In Nova Scotia 

 however it appears to be poisonous to cattle and to give rise to 

 a disease of the liver, and another species in S. Africa produces 

 similar effects. I have seen this plant growing in rough pastures 

 in such masses that one would hardly expect any cattle to survive 

 if it were really poisonous in this country. It is fortunately 

 not one of the most difficult weeds to exterminate. One of 

 the most destructive plant pests is the prickly pear in Australia, 

 where it is said to cover 1,000,000 acres of fresh land every 

 year and no satisfactory cure has yet been found. The wart 

 disease in potatoes was first noticed in 1878, but has now 

 spread over a considerable portion of this country. Fortunately 

 some varieties are immune and these should be grown. In 

 this connection it is interesting to note that the Potato was 

 first tasted by Europeans in 1519, in Brazil, by Magellan, who 

 sailed from Spain and stayed there for some months. One 

 wonders what these potatoes were like. The first picture of 

 the potato plant is found in the first edition of Gerarde's 

 Herbal, 1597, and the tubers look rather small and would 

 probably now be much despised. I exhibited a copy of this 

 book to the Club some time ago. 



GEOLOGY. 



The knowledge of the earliest fossil plants has made con- 

 siderable strides in recent years owing chiefly to the discovery 

 of well preserved specimens in the early Devonian rocks at 



