256 DISEASE IN PLANTS. 



showed that a sunflower head is profoundly altered 

 by pricking the centre of the torus, and Molliard 

 got double flowers by mechanical irritation. 



Notes to Chapter XXVII. 



For the details and classification of the multitude of facts, 

 the student is referred to Masters' Vegetable Teratology, 

 Ray Society, 1869, and the pages oi \}s\^ Gardefiers' Chronicle 

 since that date. 



Concerning torsions, etc., the student should read De Vries, 

 " On Biastrepsis in its Relation to Cultivation," Ann. of Bat., 

 Vol. XIII., 1899, p. 395, and " Hybridising of Monstrosities," 

 Hybrid Conference Report., Roy. Hort. Soc, 1900, Vol. 

 XXIV., p. 69. 



The reader will find an excellent account of the abnormali- 

 ties in flowers due to the action of parasitic insects and 

 fungi in Molliard, " Cecidies Florales," Aim. des Sc. Nat.., 

 Ser. VIII., Bot., T. i, 1895, p. 67. 



f 



