DISEASES OF GREENHOUSE PLANTS. 



269 



winter spores may be present in the soil used for striking 

 the cuttings, or on the leaves of the cuttings, and these 

 have given birth to the Bust. The worst of pests of this 

 kind is their presence is not discovered until too late to 

 prevent them injuring the foliage. The spores, when ger- 



^-Cr't^>■^ . 



• [Photo: H. A. Smith. 



CHRYSANTHEMUM RUST. 



The dark spots ou the back pi' the leat *.,are the pustales of the fungus 

 (Puccinia hieraeeii). ' - 



minating, penetrate the delicate leaf tissues with their 

 mycelium, rupture the cells, and put a stop to the develop- 

 ment of the leaf. The brown spots really indicate the 

 fungus in its full stage of development; they are the fruit 

 of the fungus. 



