M. C. INIontagne on Ctenodus Labillai-dieri. 267 



another conceptacular fructification not less remarkable, and 

 which must be very rare, since no one has hitherto described it. 

 It is however that of one of our commonest Alg?e ; I mean Geli- 

 dium corneum. I think I showed you the analysis I had made 

 on yom- late \dsit to Paris. In many dozens of individuals from 

 diflFerent localities which exist in my herbarium, one only had 

 conceptacular fruit ; all the rest were either barren or had tetra- 

 spores. In his ^Algse Mediterranei Maris,' M. J. Agardh ex- 

 cuses himself for not describing it ; because, he says, he has not 

 got it at hand. This fructification however deserves to be known, 

 and I am going to endeavour to give you an idea of it, which I 

 am sorry that I cannot accompany with a figure to make you 

 understand it more easily. 



The conceptacles of Gelidiinn corneum, which may be consi- 

 dered as the ty|:)e of the genus, are developed in the ultimate 

 pinnules which they terminate, so that the base of the pinnule 

 forms a sort of peduncle, and the tip a mucro, which however is 

 sometimes wanting. If by two parallel incisions made in the di- 

 rection of the axis, one obtains a very thin slice of the centre of 

 the conceptacle, and after carefully separating it from the lateral 

 portions it is placed on the two plates of glass in Schick's com- 

 pressor, it appears under the microscope that the centre is tra- 

 versed by a sort of columella. This, formed by the termination 

 of the filaments which occupy the centre of the fronds and of the 

 branches, in a word by the medullary tissue, presents in this re- 

 spect a sort of analogy with the organ of the same name in the 

 capsule of mosses. From all points of its circumference there 

 proceed numerous short branches which bear at their tips a little 

 group of cells of the most delicate tissue, and of such extreme 

 transparence that one can see them only by varying the intensity 

 of light by means of the diaphragms of the instrument. The 

 cells in question, at first almost spherical (at least there are some 

 of this form mixed with the rest), become gradually oblongo- 

 claviform as they increase. It is in their cavity that the spores 

 are developed, but there are a great nimiber which remain barren 

 and consequently transparent. The spores, M'hich are pyriform 

 and of a deep purple, are innumerable, and placed horizontally 

 round the central columella, fi-om whence they radiate towards 

 the walls of the cell, and to Avhich they remain for a long while 

 fixed by their more slender extremity. This disposition calls to 

 mind the unilocular capsule of some Caryo'phjllece, traversed by 

 a central placenta. I am only speaking as regards form. As the 

 conceptacle has no natural aperture, at least in the individual be- 

 fore me, it appears probable that the spores are not dispersed till 

 the decay of the plant. 



I forgot to tell you, in order to complete my obsei-vations on 



T2 



