80 BOTANY. 



epidermis early in the spring, and appear then as little spikes 

 of a rusty red color. If they are kept wet for a few hours, 

 they enlarge rapidly by the absorption of water, and may reach 

 a length of four or five centimetres, becoming gelatinous in 

 consistence, and sometimes almost entirely hiding the surface 

 of the "apple." In this stage the fungus is extremely con- 

 spicuous, and may frequently be met with after rainy weather 

 in the spring. 



This orange jelly, as shown by the microscope, is made up of elongated 

 two-celled spores (teleuto spores), attached to long gelatinous stalks (Fig. 

 47, _B). They are thick-walled, and the contents resemble those of the 

 cluster-cup spores described above. 



To study the earlier stages of germination it is best to choose specimens 

 in which the masses of spores have not been moistened. By thoroughly 

 wetting these, and keeping moist, the process of germination may be 

 readily followed. Many usually begin to grow within twenty- four hours 

 or less. Each cell of the spore sends out a tube (Fig. 47, (7), through an 

 opening in the outer wall, and this tube rapidly elongates, the spore con- 

 tents passing into it, until a short filament (basidium) is formed, which 

 then divides into several short cells. Each cell develops next a short, 

 pointed process, which swells up at the end, gradually taking up all the 

 contents of the cell, until a large oval spore (sp.) is formed at the tip, 

 containing all the protoplasm of the cell. 



Experiments have been made showing that these spores do 

 not germinate upon the cedar, but upon the hawthorn or crab- 

 apple, where they produce the cluster-cup stage often met with 

 late in the summer. The affected leaves show bright orange- 

 yellow spots about a centimetre in diameter (Fig. 47, D), and 

 considerably thicker than the other parts of the leaf. On the 

 upper side of these spots may be seen little black specks, which 

 microscopic examination shows to be spermogonia, resembling 

 those of the lichens. Later, on the lower surface, appear the 

 cluster cups, whose walls are prolonged so that they form little 

 tubular processes of considerable length (Fig. 47, E). 



In most rusts the teleuto spores are produced late in the summer or 

 autumn, and remain until the following spring before they germinate. 



