304 USTILAGINEAE. 



in height without becoming materially broader, and maintains 

 therefore the form of a cylinder pointed at the upper end. 

 Where the parts below approach the wall, columella, and spore- 

 mass, they assume their structure and colour. In other words, 

 each of the three portions grows from its base by addition of 

 new tissue-elements, which are constantly being produced and 

 pushed onwards from a basal formative tissue, and are differen- 

 tiated and assume their ultimate form in the order in which 

 they are produced (Fig. 164, C and D). The development 

 and mature structure of the spore-mass are the same as those 

 of Ustilago, which will be described presently. The wall in 

 its fully developed state is a thick coat formed of many irregular 

 layers of small round cells not very firmly united together. 

 These cells are formed in the same way as the spores from 

 the hyphae of the primary tissue, and are of about the same 

 size as the spores with a delicate colourless membrane, and 

 for the most part with watery hyaline contents. The columella 

 has the structure of the wall, but it usually incloses in its tissue 

 evident brownish fragments of the tissue of the ovule, and 

 consists at its uppermost extremity of much larger, firmer 

 hyaline cells, the origin of which I am unable to explain. I 

 may also observe that the upper extremity in young specimens 

 always ends blindly in the spore-mass {C), but in some older 

 ones reaches to the apical portion of the wall and passes into 

 it {D); it is still uncertain whether this is a difference in the 

 individual plants or a difference of age. 



" The spore-receptacle which has now been described is formed 

 only from the ovule. The perianth and stamens of the flower 

 continue in their normal state. The wall of the ovary and the 

 style are also not attacked by the fungus ; they do not follow the 

 growth of the spore-receptacle, and as this advances the lateral 

 wall is distended and at length bursts transversely ; the style 

 with the upper portion of the wall dries up into a small point 

 at the apex of the receptacle, which is borne by the latter as 

 it grows out of the perianth {A). The wall of the spore- 

 receptacle, especially where it is covered above by the withered 

 remains of the wall of the ovary, is very fragile, and tears 

 asunder at the slightest touch to discharge the spores (B)." 



The dark-violet spores have a finely-warted exospore. 

 According to Brefeld, they germinate in water after a resting 



