174 CRYPTONEMIACE^. v. 



IX. GIGARTINA. Lamour. (J. kg. ref.) 



Frond carnoso-cartilaginous, flat or cylindrical, simple or variously branched, 

 composed of two strata of cells ; the medullary stratum of cylindrical, articulated 

 filaments, anastomosing into a very lax net-work ; the cortical of moniliforra, 

 vertical, dichotomous filaments set in firm gelatine. Conceptacles external, globose, 

 finally perforate, containing within a saccate placenta ( ?) formed of closely inter- 

 woven filaments, a compound nucleus consisting of many confluent nucleoli or 

 masses of roundish-angular spores. Tetraspores collected into dense, sub-prominent 

 sori, lodged beneath the superficial cells, roundish, cruciate. 



Fronds very variable in external habit, sometimes filiform, and either pinnated 

 or dichotomously multifid : sometimes compressed or channelled on one side, some- 

 times completely flat. The flat species are often expanded into broad, leaf-like, 

 simple or proliferously ramose fronds. The substance in all is thick, between 

 fleshy and cartilaginous, elastic and generally tough when recent ; firm, crisp, and 

 somewhat horny when dry. The structure in all is very similar, the inner stratum 

 of the frond consisting of a very lax network of filaments traversing a pellucid 

 gelatine ; the outer of vertical, dichotomous, moniliform filaments issuing from 

 the outer meshes of the internal network. (See Plate XXVII. G.fig. 3.) 



This genus, as reconstructed by Prof. J. G. Agardh, is very closely related on 

 the one hand to Iridcea and on the other to Chondrus. From the former it is 

 only to be known by having its nuclei lodged in external conceptacles, instead of 

 being wholly immersed in the frond ; from the latter by the same character, and 

 by having the nucleus protected by a closely woven coccoon-like plexus of fila- 

 ments. Some of the species have the external habit of Chondrus, in which genus 

 they were formerly placed, and others as strongly resemble species of Iridcea. 



Sect. 1. Eu-gigaetina. Fronds linear, compressed or subterete, pinnately com- 

 pound. Conceptacles sessile, marginal on the pinnules. 



1 . GiGARTiNA canaliculata, Harv. ; frond linear, concave on one surface, convex 

 on the other, naked below, forked or irregularly branched beyond the middle ; 

 branches distichously pinnate or bi-pinnate ; pinna3 patent ; pinnules short, spine- 

 like, divaricating ; conceptacles formed in abbreviated, spiniferous pinnre. Harv. 

 in Beechey Voy. p. 490. J. Ag. Sp. Alg. 2, p. 272. Chondroclonium canalicidatum, 

 Kutz. Sp. Alg. p. 741. (Tab. XXVII. C.) 



Hab. Shores of California, Douglas, Coulter, Capt. Pike (26, 30.) (v. s. in Herb. 

 T. C. D.) 



