FUNGOID PESTS OF CULTIVATED PLANTS. 6 



or in proximity, sometimes on the opposite side of the leaf. These have 

 the form of minute embedded cells, containing very small hyaline spore- 

 like bodies called spermatia, whilst the cells which contain them are 

 spermoyonia. What their function may be is as yet only conjectural, but 

 they are nearly always present, and, presumably, not without a purpose. 

 Later on in the summer the same leaves, or others, develop on either or 

 both surfaces small brownish pustules, at first covered by the cuticle, but 

 at length splitting irregularly and exposing a powdery brownish dust- 

 like mass of nearly globose spores, each spore borne at first at the apex of 

 a short hyaline thread, these threads arising from a cushion-like base of 

 mycelium. These powdery spores constitute the " rust," or uredospores 

 (PI. II. fig. 226), and with them ends the second stage of the fungus ; but 

 how they are evolved from the first stage, or how they produce the third 

 stage, is a mystery still. 



The third is held to be the complete or perfect stage, and the spores 

 produced are teleutospores, or final spores. These teleutospores are more 



FlG. 1. ^ECIDIOSPORE GERMINATING. 



or less elongated, divided by a septum across the middle into two cells, 

 and supported upon hyaline sporophores or spore-bearing threads (PI. II. 

 fig. 22c). They are produced in pustules similar to those of the uredo- 

 spores, but often more compact, and are sometimes mixed with them. 

 A few of the teleutospores will sometimes be found growing within the 

 pustules of the uredospores. When the teleutospores are mature they 

 do not always germinate at once, but a period of rest supervenes, and 

 perhaps they may not germinate until the following spring, becoming, in 

 fact, veritable resting spores. This is an important fact to be borne in 

 mind by the cultivator. 



Each cell of the teleutospore is capable of sending out a germ tube 

 through a special pore, and as this germ tube grows, the contents of the 

 cell of the teleutospore passes into the germ tube, known also as the 

 promycelium, and to the extreme end. Ultimately a septum, or division, 

 crosses the tube and prevents retreat. One, two, or more additional 

 divisions of the apical cell take place, and from the side of each of 

 these newly constituted cells buds or processes appear, which gradually 

 enlarge, and in time are converted into secondary spores, or promycelial 



