THE BEGINNINGS OF II FE. 339 



although most positive statements have from time to 

 time been made by different observers concerning their 

 heterogenetic origin, by changes similar to those which 

 convert the milk-globule into a Fenkillium and the 

 globules of many plants into Amylobacters ^. Thus^ in 

 speaking of one of the commonest blights, that pro- 

 duced by Uredo^ M. Turpin says-: — 'II m'est bien 

 demontre par un grand nombre d'observations, faites 

 sur diverses plantes plus ou moins attaquees de ?Ure- 

 dinee, que la carie n'est qu'un etat morbide^ qu'un 

 degenerescence de la globuline ou fecule du tissu ccllu- 

 laire du perisperme du graine du ble.' A similar 

 change, however, may also occur in the globules which 

 naturally exist in the cells of the stem or in those of 

 the leaves ; so that_, according to Turpin, ' L'Uredinee 

 est une maladie qui attaque par place, les globules 

 contenus dans les vesicules du tissu cellulaire des 

 plantes, qui leur donne quelquefois plus de volume et 



^ It has been noticed that the leaves of many plants, prior to the 

 appearance of fungi within them, have been remarkable for their 'almost 

 unnatural green colour;' and, according to Mr. Cooke (loc. cit., p. 155), 

 ' this phenomenon has been noticed in ears of com, in which every grain 

 was soon afterwards filled with spores of bunt.' This fact is one of 

 much interest and importance, since it will be subsequently shown (in 

 Chaps. XX and XXI) that the same extremely bright green colour is 

 almost invariably to be observed amongst- those portions of Algce, or 

 amongst EuglencB and DesmidicB, which are about to undergo a hetero- 

 genetic change ; and in these latter cases every step of the process of 

 transformation into new organisms may be watched by the micro- 

 scopist. 



2 Loc. cit., p. 346. 



Z 2, 



