135 
1917-18.] Phycomycetous Fungi. 
and by Williamson (13) without any explanation being advanced for their 
use of the term. Previous to this, Cash and Hick (1) had indicated that 
the globules found by them in attachment to the hyphse of their fungus 
were probably oogonia, and in all probability they were correct, but the 
structures at present under consideration are widely different. It is not 
correct to assign the term “ oogonia ” to globular expansions, each of which 
occurs in close proximity and attachment to two or three others of the 
same kind, each devoid of a partition- wall separating it from the supporting 
hypha, and each possessed of a membrane indistinguishable from the 
membrane of the vegetative hyphse. They may be regarded either as 
intercalary sporangia, such as are found, for example, among the Chytri- 
dinese in Physoderma, or they may be structures formed ' by the fungus to 
take fullest advantage of favourable metabolic conditions. The formation 
of intercalary sporangia is a frequent phenomenon among modern fungi, 
and the regularity in the shape and the uniformity in the size of these 
bodies on the whole favours this interpretation of their nature. 
II. Terminal and Solitary Vesicles (Plate, fig. 2). 
In Plate, fig. 2 is shown a markedly different type of structure, examples 
of which were found in a tangential longitudinal section of the cortex of 
Lepidodendron aculeatum (Upper Foot Mine : Lower Coal Measures). Its 
characteristics are the following : — 
