CONIOTHECIUM. 



[ 166 ] 



CONJUGATION. 



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

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

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

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

 see Hassall, On the Coloration of the Ser- 

 pentine, Botanical Gazette, no. 20, Auff. 

 1850. 



CONIOTHECIUM, Corda.— A genus of 

 Tondacei (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 gromng in the 

 cracks of dead wood (elm), composed of 

 minute free membranous peridia enclosing 

 numerous spores, which escape by the burst- 

 mg 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- 

 cese, the Desmidiacese, the Diatomacese, the 

 Palmellaceae, and doubtfully in the Sipho- 

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

 gites. 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 cells into 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. 



137. 



Zygnema cruciata. 



Conjugating filaments. 



Magnified 250 diameters. 



Fig. 138. 



confluent by the ab- 

 sorption of the surfaces 

 of contact (fig. 13/). 

 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 

 both cells collect in the 

 cross-piece, this is the 

 case also in Meso- 

 carpus (fig. 138j 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. 

 (See Zygnemace^.) 



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. 



Mesocarpus scalarls. 



Conjugating filaments 



with spores. 



Magnified 200 diameters. 



IMougeotia genuflexa. 



Conjugating filaments. 



Magnified 100 diameters. 



place until the single cells of the filaments 



