DEFINITIONS. 
xii 
the other margin free. When calyciform, it is first entire and 
globose, at length opening with an entire or laciniated margin, 
forming a cup, which contains the sporangia. Often the margin 
or lobules of the frond is changed in texture, and forms an acces- 
sory indusium, with which the interior, lateral, attached, special 
indusium more or less connives, and by their union ‘they form a 
vertical or reflexed, continuous or urceolate, calyciform or bila- 
biate, marginal cyst, which contains the sporangia, and is open 
exteriorly. Sometimes the whole of the sori of each segment are 
included within a universal indusium, which is formed by the 
revolute margin of fertile contracted fronds. 
