DI-MORPHISIT. 41 



sporidia. Here vegetation ends in tlie artificial 

 culture above indicated. 



When the sporidia are sown upon the epidermis 

 of a favourable plants the germ-tube being emitted^ 

 penetrates the wall of any approximate celhile, 

 swells and increases into a cylindrical tube equal in 

 thickness to the original sporidia, and therefore 

 four or five times the diameter of the germ-tube 

 before it entered the cellule. The contents of the 

 sporidia and external portion of its germ-tube pass 

 into the portion within the cellule, and then these 

 external portions perish, and all evidence of the 

 entry is obliterated, except a very minute point at 

 which the tube remains attached to the inner sur- 

 face of the wall of the cellule. The enclosed tube 

 soon elongates, divides, and becomes branched. 

 These branches perforate the inner walls of the 

 epidermis, and pass into the intercellular spaces of 

 the parenchyma to become mycelium. This takes 

 place within 24 hours. A few days afterwards 

 the mycelium is spread through the parenchyma. 

 At length the surface of the same spots which had 

 been sown in the first instance with the sporidia, 

 become of a whitish tint, rapidly increasing and 

 intensifying. Three days after, little protuberances 

 appear on the surface of the white spots. These 

 are of an orange colour, and many of them are 

 surmounted by a Httle drop of mucilaginous fluid. 

 These are spermogones. Their number daily in- 

 creases, and a little time after appear numerous largo 



