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FERNS : SYNOPTICAL LIST— LVI. 



Synoptical List, with descriptions, of the Ferns and Fern- Allies of Ja- 

 maica. By G. S. Jenman, Superintendent, Botanical Garden, 

 Demerara. 



Order IV, — Selaginellacece, 

 Sporangia of two kinds, larger and smaller ; the former (macrospo- 

 rangia) containing macrospores ; the latter (microsporangia) containing 

 microspores ; borne separately in the axils of normal or modified leaves, 

 in which they are single, and free or partially embedded; the macrospo- 

 rangia being calcareous-white and inferior in situation to the microspo- 

 rangia. 



This order consists of two very dissimilar genera if only the physiog- 

 nomy or conformation of the respective members be regarded. They 

 are associated however by the character which they possess in common, 

 of the sporangia and spores being of two kinds, one larger than the 

 other, generally considerably larger ; each kind of the spores possessing 

 separate sexual potentiality, generation resulting from the interaction 

 of the contents of the cells that are produced on their germination ; if 

 this union is not affected the antecedent germs perish. 



Fructification in terminal spikes in the axils of imbricating keeled 

 bracts ; leaves usually dimorphons. 



1. Selaginella. 



Fructification embraced in the clasping case of the normal leaves ; 

 the plants loiBotte-like in form. 



2. Isoetes. 

 Genus I. Selaginella, Beauv- 



Sporangia bivalved, uniform, orbicular, or subglobose, borne in modi- 

 fied 4-gonal spikes, at the end of the branches ; macrosporangia inferior, 

 usually few, containing few large white macrospores ; microsporangia 

 superior, usually numerous, containing multitudinous minute micro- 

 spores ; leaves small or minute, generally of two kinds — rarely of one- 

 major and minor, each kind bi-serial, imbricating or slightly apart, the 

 larger series lateral and spreading from the axis obliquely or horizon- 

 tally, the smaller intermediary, more or less in a line with and dorsal 

 on the axis and appressed thereto ; fronds generally pinnately or 

 irregularly divided, rarely simple, often decompound ; more or less 

 copiously leafy throughout; prostrate, sub- erect, erect or scandent. 



Selaginellas differ from their allies the club-mosses by possessing two 

 kinds of sporangia and spores, the generally distichous arrangement of 

 the leaves, which gives the stems a flattened appearance, their more or 

 less prostrate or subscandent habit of growth, their uniformly commu- 

 nal association and, as a rule, terrestrial location. Three or lour Lyco- 

 podia have a somewhat similar arrangement of their leaves, and a con- 

 siderable number are terrestrial, and some too are communal, but among 

 the selaginellas these are nearly constant characteristics. In a few 

 species, none of which is native within the limits of this flora, the leaves 

 are all of one kind and multifarious, the stems being consequently con- 

 volute, as is the ride in the Lycopodia. In nearly all the species there 

 is some variation of shape in the fronds, and in many this is consider- 

 able. 



