SCIENTIFIC COMMITTEE, APRIL 11 



lxi 



beast, or vegetable, unless all our evolutionary theories are hopelessly 

 wrong. Most cultivated plants must suffer from the absence of a struggle 

 for existence and from one-sided selection. It might be possible to delay 

 the deterioration by severe treatment, by change of soil and climate, and 

 other methods. The survivors after such a treatment should be more 

 vigorous than any selected at random for propagation. 



A plant has an organised, correlated body, and reacts distinctly 

 to change of climate. This reaction involves a one-sided development. 

 I fail to see how a flowering plant can escape the common enemy — old 

 age. Where are the potatoes of thirty years ago '? 



Mr. Sutton said that in his experience deterioration of potatoes does 

 take place sooner or later, the only well-niarked exception to this rule 

 being the ' Early Ashleaf.' which is now apparently as vigorous as it has 

 ever been. Potatoes raised from seed show marked variation on every 

 point, some deteriorating within five or six years, others not until the 

 passage of a much longer period. 



Mr. Lindsay of Marrayfield, Midlothian, sent tubers of ' Maincrop ' 

 potatoes and of Solatium etuberosum raised from tubers planted out in 

 ordinary unmanured garden soil in 1899. the plants having remained in 

 the open ground unprotected and undisturbed, except for moving once 

 in September 1902. The plants had not suffered from any kind of 

 disease nor from frost, and do not appear to have deteriorated in any way. 

 The question of the influence of the moister Scotch climate on the 

 potato was raised, and the effect of flower and seed production on the 

 vigour of the tubers produced was discussed. 



Rust on Rose. — Dr. Cooke reported as follows on this well-known 

 trouble : — " This rust was known half a century ago as Credo ping u is, 

 but afterwards as Colcosporium pingue, and was then considered to be 

 an independent fungus. In more recent times it has been found that 

 most of these parasites exist under three forms, or pass through three 

 stages, viz. — (1) .Eoidium. i/2) Uredo, (3) Teleutospore. In the present 

 instance (1) the aecidium form is Coleosporium pingue, (2) the uredo 

 form is Leeyihea rosce, and (3) the teleutospore form Phragmidium 

 subeortieatum. The Coleosporium is the first form to appear in the 

 spring, on the twigs and peduncles chiefly ; near midsummer the uredo 

 spores appear on the leaves ; in autumn the teleutospores appear as black 

 tufts on the under surface of the leaves. As an endophyte this pervades 

 the tissue of the entire plant, and is very difficult .to combat. It is 

 recommended that all the affected spots be cut off as soon as they are 

 recognised, and burnt, so as to prevent the dispersal of the spores. 

 Before the buds expand in the spring, bushes that have been attacked 

 the previous year should be well syringed with Bordeaux mixture. Leaves 

 should be watched carefully through the summer, and when the uredo 

 appears thereon, or later the teleutospores, the leaves should be picked 

 off and burnt, because when the teleutospores germinate they are able 

 to infect healthy roses, and produce the Coleosporiurn in the following 

 spring. Occasional syringing with Bordeaux mixture checks both the 

 first and second stages.'* 



Diseased Arums. — Mr. Saunders reported that he was able to find only 

 a few springtails and two very minute worms in the tubers, and he 



