CONIOTHECIUM. 



[ 166 ] 



CONJUGATION. 



mum Thompsoni, Ralfs, Ann. Nat. Hist. 2 ser. 

 vol. v. 336. pi. 9. 3. Anabaina Flos-aquce, 

 Harvey, Brit. Algee, ed. 1 ; Hassall, Brit. 

 Fr. Algce, t. 75. f. 2. For further details, 

 see Hassall, On the Coloration of the Ser- 

 pentine, Botanical Gazette, no. 20, Aug. 

 1850. 



CONIOTHECIUM, Corda. A genus of 

 Torulacei (Coniomycetous Fungi), apparently 

 somewhat doubtful plants. Berkeley and 

 Broome name three of Corda's species as 

 occurring in Britain. 



BIBL. Berk, and Broome, Ann. Nat. Hist. 

 2 ser. v. 460; Corda, Icones Fung. i. figs. 21, 

 25, 26 ; Fries, Summa Veget. 523. 



CONIOTHYRIUM, Corda. A genus of 

 Sepedonei (Coniomycetous Fungi). 



C. glomeratum, Corda, recorded by 

 Berkeley and Broome as British, is said by 

 Fries to belong to his genus Clisosporum. 

 It is a microscopic plant growing in the 

 cracks of dead wood (elm), composed of 

 minute free membranous peridia enclosing 

 numerous spores, which escape by the burst- 

 ing of the apex. 



BIBL. Berk, and Broome, Ann. Nat. Hist. 

 2 ser. xiii. 460; Corda, iv. f. 208; Fries, 

 Summa Veget. 522; see also Montagne, Ann. 

 des Sc. nat. 3 ser. xii. 304. 



CONJUGATION. A process occurring 

 among some of the lower plants and animals, 

 in which the substance of two distinct orga- 

 nisms comes into contact and becomes fused 

 into a single mass. This operation is always 

 connected with reproduction in plants, and 

 probably also in animals. 



In the vegetable kingdom it has been 

 observed in the Algae, viz. in the Zygnema- 

 ceae, the Desmidiacea?, the Diatomacese, the 

 Palmellacea3, and doubtfully in the Sipho- 

 nacea3, and in one genus of Fungi, viz. Sizy- 

 yites. In all these cases it consists essen- 

 tially in the blending together of the contents 

 of two distinct cells, either by the complete 

 fusion of two free cells, by the passage of 

 the contents of one cell into the cavity of 

 another, or by the emission of the contents 

 of both cellsinto a space between them, where 

 the mixed contents become enclosed in a 

 special envelope. 



The conjugation earliest discovered was 

 that of the Zygnemacese, in which the cells 

 of distinct filaments lying parallel with one 

 another, become united by lateral inoscula- 

 tion or by cross branches, formed by the 

 budding out of the walls of the cells opposite 

 to each other, the protruded processes 

 coming into contact, cohering and becoming 



Fig. 138. 



confluent by the ab- Fig. 137. 



sorption of the surfaces 



of contact (fig. 137). 



The cavities of the two 



cells being thus freely 



opened into one 



another, the contents 



become mixed ; in Spi- 



rogyra and Zygnema 



the contents of one of 



the cells usually travel 



across into the cavity 



of the other (PI. 5. 



fig. 18) ; in Zygogo- 



nium the Contents of Zygnema cruciata. 

 both Cells Collect in the Conjugating filaments 



cross-piece, this is the M mfied 250 diameters . 

 case also in Meso- 

 carpus (fig. 138) and Staurocarpus, in the 

 latter of which the 

 cross-piece becomes 

 greatly enlarged. The 

 contents in all these 

 cases become retracted 

 from the cell-wall, and, 

 secreting special coats, 

 become spores, which 

 escape by the rupture 

 of the conjugated cells. 

 In Mougeotia (fig. 139) 

 there is no cross branch. 

 The filaments become 

 angularly bent and in- 

 osculate at the angles. 

 A spore is said to be 

 formed in each cell here. Ma ^ fied 200 diameters . 

 (See ZYGNEMACESE.) 



In the Desmidiacese the process presents 

 a number of modifications. In the filamen- 

 tous forms, such as Hyalotheca and Didy- 

 moprium, conjugation does not usually take 



Fig. 139. 



Mougeotia genuflexa. 



Conjugating filaments. 



Magnified 100 diameters. 



place until the single cells of the filaments 



