20 INTRODUCTION. 



by little. It is perfectly homogeneous; it is but when 

 it commences to decompose that it takes on a granular ap- 

 pearance ; but it never presents those longitudinal striae which 

 I have remarked in that of Conferva and Zygnema. 



I have not perceived any motion in the granules of the en- 

 dochrome, excepting in the case of the rupture of a filament. 

 The granules escape then in jerks ; they often collect them- 

 selves .into pellets, and sometimes the mucilage which ac- 

 companies them forms about them a species of membrane ; 

 but these masses of granules have never appeared to me 

 susceptible of organization into reproductive corpuscles ; in a 

 word, never have I seen them germinate. 



The solubility of these granules in alcohol indicates their 

 resinous nature. Sulphuric acid diluted with water con- 

 tracts them into the centre of the filament to a faint ribbon 

 of a brownish green. When this reagent is employed of 

 greater strength, the granules resolve themselves into a 

 mass of a blackish green ; but the external membrane resists 

 the action of the acid. If recourse is had to ammonia, it 

 often happens that, by a phenomenon of endosmosis, the fila- 

 ments empty themselves entirely of their granules. This is 

 seen especially in the spores which have commenced to ger- 

 minate; the granules all issue by the extremity of the 

 filament in germination, and the external membrane, which 

 was not before visible but at the extremity of this filament, 

 remains entirely empty like to a glass ball. The ammonia 

 possesses also the singular property of imparting a light pink 

 coloration, or vinous red, to certain parts of Vaucheria, par- 

 ticularly to the superior extremity of the spore, when it is at 

 the instant of quitting the mother plant, and this part is 

 less furnished with endochrome than the rest. 



If I have not indicated up to the present time to what 

 species of Vaucheria the observations which I have described 

 apply, it is because the species of this genus are esta- 

 blished upon bad characters. In truth, the organization of 

 the spore, such as I have described it, applies to Vaucheria 

 ovata D. C. = Vaucheria clavata D. C. et linger ; for I have 

 found once, upon the same filament, both this form 

 and that which has been named Vaucheria sessilis. A 



