PINE-BLISTER. 



In the months of April and May, the younger 

 needle-like leaves of the Scotch pine are occasionally 

 seen to have assumed a yellow tinge, and on closer 

 examination this change in colour, from green to 

 yellow, is seen to be due to the development of 

 what look like small orange-coloured vesicles or 

 blisters standing off from the surface of the 

 epidermis, and which have in fact burst through 

 from the interior of the leaf (Fig. 37). Between 

 these larger orange-yellow blisters the lens shows 

 certain smaller brownish or almost black specks. 

 Each of the vesicular swellings is a form of fungus- 

 fructification known as an jEcidiuni^ and each of 

 the smaller specks is a fungus-structure called a 

 Spermogonmm^ and both of these bodies are 



