330 



GEEENHOUSE MANAGEMENT. 



like particles. The pustules are often an eighth of an 

 inch or even more in length, and are of an elliptical, 

 oval, or sometimes of a crescent shape, and form ou 

 both sides of the leaves and even on the stems (Fig. 114). 

 Tha spores are of two kinds, one of which, the 

 uredospores (Fig. 115 a), are round or elliptical, and show 

 a few scattered spines under the miscroscopc. They 

 will germinate at once if they fall on a moist surface and 

 if the moisture is on a carnation plant, the germ tubes 

 will penetrate the epidermis, and work their way among 

 the tissues, break down the cells, absorb the juices and, 

 having made their growth, develop a new mass of spores, 



f?\ ffi&tf^ <*5fc ^ **, ^ 1US com pl°tmg a cycle in per- 

 W ^W t/f/fP haps two weeks. The other 

 -& spores, known as teleutospores 

 (Fig. 115, b), are somewhat 

 darker in color than the others, 

 and are more oval in shape, be- 

 sides lacking the spines found 

 upon the uredospores. Some 

 varieties seem more subject to 

 this disease than others, and 

 plants with firm tissues are less 

 likely to be attacked than others of the same variety 

 with soft watery leaves. As water is required for the 

 development of the fungus, syringing should only be 

 done on sunny days and in the morning, that the plants 

 may dry off before night. In damp weather, the 

 ventilation should be thorough, and if moisture stands 

 on the plants, the fire heat should be increased. 



To grow plants free from rust, they should be of a 

 strong constitution and from a healthy stock. Prefer- 

 ably, as stated in the chapter upon carnation culture, 

 they should be taken from plants that have not been 

 long in flower, and that have not been grown in a high 

 temperature. 



FIG. 115. SPORES OF CAU- 

 SATION RUST. 



