ARCHER — ON ZYGOGONIUM. . 119 



define it, especially as the genus Mougeotia (de Bary) is not at all the 

 same thing as Mougeotia (Ag.), being in fact another instance of what 

 I regard, as I before mentioned, as a thing to be regretted — that of the 

 revival of an old name in a new sense. 



The type of the genus Mougeotia (Ag.) is the ordinary M. genuflexa 

 (Ag. et Auct.), remarkable for the curious manner in which the fila- 

 ments come into contact, and become mutually attached at the obtuse 

 angles formed by the knee-like bending of the joints, the true conjuga- 

 tion, however, taking place, as shown by de Bary, by the union of the 

 contents of a joint with those of a neighbouring joint of the same fila- 

 ment by means of an arch- or bridge-like communication formed between 

 them, a portion of the so-united contents, poor in endochrome, being 

 shut off in each parent-cell, the central portion contained in the arch- 

 like connexion becoming the spore. This is, the latter circumstance 

 excepted, similar to the mode which takes place in the false genus Bhyn- 

 conema, as compared with that of Spirogyra. From the circumstance 

 alluded to, and inasmuch likewise as the contents of the ordinary joints 

 form a compressed band, like that of Mesocarpus, de Bary is surely cor- 

 rect in referring Mougeotia genuflexa ( Ag. et Auct.) to that genus, which 

 he does under the name Mesocarpus pleurocarpus. (Why not, however, 

 under the name Mesocarpus genuflexus ?)■ 



Now, the type of de Bary's new genus Mougeotia — for new genus it 

 must be regarded, though called by an old name — is the plant named by 

 him Mougeotia glyptosperma. This is a very beautiful and very marked 

 plant, found in spring, rather abundantly conjugated, in certain heath 

 pools. This plant, as de Bary well points out, could not be placed 

 alongside of Mesocarpus pleurocarpus, ejus (= Mougeotia genuflexa Auct.), 

 nor could it be referred to Mesocarpus (Hass.) at all, (though it may 

 possibly have been previously recorded under the name Mesocarpus in- 

 tricatus). It is no doubt related on the one hand to the latter genus : 

 like it, the endochrome forms a compressed longitudinal band ; and like 

 it, too (so far as the circumstance is of value), the zygospore is formed 

 halfway between the two conjugating joints ; but it is distinguished 

 strongly by the fact that here the whole cell-contents, " primordial 

 utricle" and all, of the two conjugating joints completely coalesce, 

 leaving the cavity of the parent joints empty, in order to form 

 the zygospore ; whilst in Mesocarpus the contact of the ' ' primordial 

 utricles" of the two conjugating joints is not followed by a fusion of the 

 whole united mass into the zygospore, but this latter is formed by a 

 concentration of the principal part of the green and solid contents in 

 the connecting canal halfway between the two conjugating joints and 

 the shutting off thereupon of the residue of the pale granular contents 

 remaining in each parent joint, which latter becomes eventually effete 

 and lost. Hence in the genus Mougeotia (deBary, non Ag.) the spore is 

 the actual result of the complete fusion of the entire of the cell- contents 

 of the two conjugating joints — it is the true zygospore, whilst in Me- 

 socarpus the spore is a further ultimate development or daughter-cell 

 formed from a portion only of the primary zygospore. Therefore, on 



