372 



OEGANOGRAPHY. 



internal mass are thus described by Henfrey : — " At an early 

 period the cells of the internal mass present the appearance of a 

 Fia 815 large number of filaments radiating from the cen- 

 ,^ ' tre of the sporangium to the wall. These soon be- 

 I come free from each other, and it may then be per- 



Ke ceived that some are of very slender diameter, 



and others three or four tiroes as thick. The 



slender ones are developed at once into the long 

 elaters {fig. 815, e) characteristic of this genus, 

 containing a double spiral fibre, the two fibres, 

 however, coalescing into one at the ends. The 

 thicker filaments become subdivided by cross par- 

 titions, and break up into squarish free cells, 

 which are the parent-cells of the spores, four of 

 which are produced in each." The sporangia in 

 this genus are situated on the under side of the 

 receptacle {fig. 813, r), and vary in form; — they 

 burst by valves. In Jungennannia the spo- 

 rangia are elevated upon stalks arising out of 

 the vaginule ; they are more or less oval in form, 

 and open by four valves which spread in a cross- 

 like form ; they contain spore-cells and elaters 

 with a single spiral filament. In Anthoceros 

 the sporangia open by two valves, and have a 

 central axis or columella ; they are of an elon- 

 gated, tubular, or conical form, situated on a 

 short stalk, and contain spore-cells and elaters, 

 but the latter have no spiral fibres in their 

 interior, and are much simpler in their structure 

 than those just described as found mMarchantia. 

 In Riccia the sporangia are imbedded in the 

 substance of the frond, and have neither elaters 

 nor columella. They have no regular dehiscence. 

 The spores have usually two coats, like the pollen-cells ; the 

 outer coat also frequently presents markings of different kinds : 

 in Marchantia, however, the spore has but one coat. They all 

 germinate without any well-marked intermediate prothallium, 

 although some produce a sort of eonfervoid mass or mycelium. 



7. Charace^ or Charas.— There is still much difference of 

 opinion among botanists as to the position of this order. The 

 Charas have been commonly placed among the Algse ; but the 

 structure of their reproductive organs indicates for them a higher 

 position. They are generally considered as intermediate in their 

 nature between Hepaticacese and Algse, while by Berkley, whose 

 opinions on all matters connected with Cryptogamous Plants are 

 eminently worthy of consideration, they have been classed with 

 the Acrogens ; and, in accordance with his views, we have also 

 placed them in that division of Cryptogamous Plants. 



Fig. 815. Elaters, 

 e, of Marchantia. 



