INTRODUCTION TO CRTPTOGAMIC BOTANY. 153 



take place, even in conjugating threads, by the formation of 

 connecting tubes. In the genus Mougeotia, and some others, 

 the threads become geniculate, and unite at the two bends, 

 sometimes indeed with, but often without, connecting tubes, 

 and according to circumstances the spore is globose, elliptic, or 

 subquadrate. In Thwaitesia, (Fig. 39,) and in at least one 

 other genus, the endochrome of the spores is divided longitu- 

 dinally and transversely, and so four new spores arise. 



12.5. Should it prove true that the spores are in many cases 

 eventually resolved into myriads of zoospores, we shall have 

 merely the same process which takes place in Ulothrix. The 

 bodies which produce the zoospores are a distinct transform- 

 ation of the endochrome, and it is very probable that such 

 bodies, in their first condition, may be capable of propagating 

 the plant, while, under other circumstances, their endochrome 

 may undergo a further change and produce zoospores. 



126. The species are extremely numerous, and exhibit very 

 great variety in the nature of the endochromes and the 

 disposition of the spores. A curious series of circular folds is 

 often formed in the outer tube where the spores are produced, 

 arising apparently from its growing faster than the contained 

 sac. This is conspicuous in many conjugate species, but no- 

 where more so than in the genus (Edogonium* which certainly 

 ought to be placed in the same series. In this latter genus 

 there is a singnLar tendency in the green spores to pass into a 

 bright red or scarlet, which is not without its parallel in earlier 

 and simpler species, as for instance in Protococcus. The 

 endochrome of the spores of Zygnema is apparently uniform, 

 but Pringsheim-f- has found that, after they have been steeped 

 for some time in oil, there are traces of a spiral structure, a 



* In CEdogonium capiUare, Kiitz., the granules of the endochrome in 

 certain stages assume a spiral arrangement, and larger granules are 

 connected with smaller. Ultimately the several spiral threads cross, 

 and form a network. Many instances of reticulate endochrome, by the 

 formation of vacuoles, occur in different groups, as Ectocarpus, Hydro- 

 dictyon, &c. See Kutzing, Phyc. Gen. tab. ii. 12; DerbSs and Solier, I.e. 

 tab. 5 ; Cohn Untersuchungen, tab. 19, &o. 



t Flora, 1852, tab. v. 



