Bibliographical Notices* 206 



through spring, summer, autumn and winter till the approach of the 

 new spring. 



2. The tube consists of a tender vegetable membrane, whose inner 

 surface is clothed, more or less thickly, with round or elongated par- 

 ticles of hardened jelly involved in chlorophyll, whence the whole 

 plant derives its lively green colour. The rest of the tube is filled 

 with a fluid, somewhat granular, slimy substance, in which, as also in 

 the globules of the chlorophyll, there is no observable motion. 



3. Under the due influence of light and temperature a peculiar 

 alteration takes place at the top of the tube and of its branches, 

 which has the closest agreement with the formation of spores in sim- 

 ply constructed plants. There originates — namely, below the tips of 

 the shoots — a transverse dissepiment in the tube, which was at first 

 perfectly continuous. This is very thin, and separates the upper por- 

 tion of the contents of the tips of the threads from that portion which 

 is below. In this upper part only a new tube is formed out of a 

 colourless, slimy, granular substance within the mother- tube, which 

 is closely pressed to it. 



4. The development of this inclosed tube resembles that of other 

 spores in their mother-cells, but it at length attains a higher order of 

 organization*, inasmuch as, instead of being formed of a simple ve- 

 getable membrane, it is, in fact, an epithelium with vibrating ciliary 

 processes. At present, however, there is scarcely a trace of organi- 

 zation in the tube itself or its contents. 



5. By means of the swelling of the ripe spore simultaneously with 

 the attenuation of the mother-tube, the tube bursts and the spore 

 pushes spontaneously through the narrow aperture, exhibiting at last 

 a revolving motion. This process, which lasts some minutes, may 

 in a certain degree be compared with that of delivery in the animal 

 kingdom. 



6. After the separation of the spores the dissepiment expands, and 

 forms a sac within the vacant tube, or a branch is given off^ imme- 

 diately below the dissepiment. In either case we have a mere pro- 

 longation of the original tube. 



7. The same process of formation takes place in the new portion 

 of the original tube, and it is repeated a third time ; but as the tube 

 is continually decreasing in diameter, the new spore is proportionally 

 lessf. 



8. The spore is an oval or elliptic body, which, when liberated 

 from the mother-tube, moves freely in water in every direction and 

 swims about like an animal. An epithelium uniformly clothed with 

 vibrating cilia incloses a slimy substance, which in part assumes 

 the form of vesicular cavities ; the epithelium is clothed within with 

 numerous globules which are invested with chlorophyll. At the 



* We follow the language of Unger, without however adopting his views 

 altogether as to the animal nature of the spores. See however on this head 

 * Berk. Gleanings of Brit. Algae/ under the article Vaucheria clavata. — Ed. 



f This is pcrliaps one of the most interesting facts contained in the trea- 

 tise, and altogether analogous with what Corda describes in the formation 

 of the spores of certain Fungi. — Ed. 



P2 



