158 



CRYPTONEMIACE^. v. 



degree. These latter genera lead us at once in structure to the Rhodymeniace^, 

 from wliich they can be known only by the structure of the nucleus. 



The sporiferous nucleus is very frequently sunk in the frond, beneath the filaments 

 of the periphery ; where it either lies suspended among those of the inner stratum, 

 or it is encompassed by a dense plexus of filaments, forming a sort of immersed 

 conceptacle, not unlike the coccoon of a chrysalis. In a few cases (as in Chrysy- 

 nienia, Chylocladia, Gigartina, etc.) it is lodged in an external globose or hemi- 

 spherical conceptacle, with or without a terminal pore ; and in Stenogramma many 

 compound nuclei lie within a linear, rib-like conceptacle, running through the 

 middle of the leaf. 



The Order naturally divides itself into two sub-orders, distinguished from each 

 other by the greater or less complication of the nucleus. These have been recently 

 elevated by Prof Agardh into the rank of Orders, but as it appears to me rather 

 unnecessarily ; the difference in nucleatic structure being one of degree only, and 

 the plants of both sub-orders having a most intimate relationship in structure and 

 habit. In our first sub-order (Gigartine^) the nucleus originates in several con- 

 gregated, fertile cells, filled at first with dense granular matter or endochrome. 

 These, as the fruit matures, enlarge, while the matter contained in each divides into 

 numerous spores ; and each original cell is thus converted into a nucleolus of spores, 

 retained within the expanded cell-wall ; which then forms (till it disappears) a 

 membranous periderm to the nucleolus. The whole nucleus, or aggregation of these 

 nucleoli, appears at first divided by pellucid lines, marking the boundaries of the 

 mother-cells ; but all traces of these generally disappear before the spores are 

 emitted, and at this advanced stage it is not always easy to recognise the proper 

 structure. In our second sub-order (Cryptokeme^) the nucleus originates in a single 

 cell, which undergoes similar changes to those just described as occurring in the 

 numerous mother-cells of the first sub-order. 



The tetraspores are either dispersed among the cellules of the periphery, or collect- 

 ed into definite, superficial, or immersed sori ; and in a few cases are formed in 

 external wart-like bodies of irregular shape, called nemaihecia. They are some- 

 times zonate, but more commonly cruciate. 



This is one of the largest Orders of Rhodosperms, and is dispersed through all 

 latitudes from the Arctic regions to the Equator. Thirty-five genera are described 

 by Agardh, twenty-thi'ee of which we already claim for the North American Flora ; 

 and probably when our coasts have been more fully examined, several others may 

 be added. 



Among the useful plants of the Order is Chondrus crispus or Carrageen, so well 

 known as an ingredient in blanc-manges and jellies ; and many others, particular- 

 ly of the genera Iridwa and Gigartina, numerous large species of which are common 

 on the Pacific coasts, have similar properties. 



