PAKMELIA. 



207 



posed of five or six oblong cellules in apposition by their 

 extremities, simple, rarely furcate. The thecae in the young 

 state are somewhat linear or narrow, but when full of mature 

 spores are broadly obovate, presenting irregular bulgings 

 corresponding to the individual spores. The thecse and pa- 

 raphyses, with the exception of the terminal cell, along with 

 the hypothecial tissue, are coloured blue by iodine. The 

 spores are somewhat small, oval, colourless, simple, almost 

 solid, excavated at their ends into two globular cavities full 

 of yellowish protoplasm ; these nuclear masses are frequently 

 united by a narrow line of the same material running in the 

 long axes of the spores. The thickened wall appears to 

 consist of cellulose, and to be caused by a deposit on the 

 interior of the epispore ; it is not coloured by iodine alone, 

 but, if sulphuric acid be subsequently added, a light blue 

 colour is developed. The terminal nuclei were erroneously 

 described by Schleiden as terminal caps, the remnants of a 

 hardened mucilaginous coating of the exterior of the spore. 

 They are the most prominent features of the spore, and are 

 frequently distinct when the spore-wall is scarcely visible. 

 Hence a theca full of nearly ripe spores often appears as if 

 studded over with a series of small yellow buttons. In 

 germinating the germ-filaments proceed from one or both 



