HOW PLAXTS OBTAIN FOOD. 



87 



of these plants wliich are known as parasitic fungi. Tlie plant at whose 

 expense tliey grow is called the ^' jLosiS' 



One of these parasitic fungi, which it is quite easy to obtain in green- 

 houses or conservatories during tlie autumn and wdnter, is the carnation 

 rust {C'7-o}fiyt\-s cayvophvilinus), since it Vjreaks out in rust)' dark Vjrown 

 patches on the leaves and stems of the carnatinn (see fig. 75). If we make 

 thin cross sections through one of these spots on a leaf, and place them for a 



Fig. 76. 

 Several teleutospores, sho^^'ing the variations in form. 



few minutes in a solution nf chlor.tl hydrate, portiems 'if the tissues of the 

 leaf will be dissolved. After a fe^^' minutes \\"e w.ish the sectirms in water on 

 a glass slip, and stain them with a solution of eosin. If the sections were care- 



Fig. 77. 

 Cells from the stem of a rusted carnation, showing the intercellular mycelium and haustoria. 

 Object magnitied 30 times more than the scale. 



fuUv made, and thin, the threads of the mycelium will be seen coursing be- 

 tween the cells of tlie leaf as slender threads. Here and there will be seen 

 short branches of these threads which penetrate the cell wall of the host and 

 project into the interior of the cell in the fmn nf an irregular knob. Such 

 a branch is a hamtorium, Y>\ means of this haustorium, wdiich is here 



