XIV. ALGM. 975 



vibrating hairs, and resembling the antherozoids of Fucacem ; the sporangium con- 

 tains green granules ; a septum forms in each organ, below the antherozoids in the 

 antheridium, and below the granular mass in the sporangium. When fertilization 

 is about to take place, these two organs bend towards each other, the antheridium 

 bursts open at the tip, the antherozoids escape, seek the extremity of the sporan- 

 gium, the top of which has also opened, enter it, and thus effect fertilization.' 

 The membrane of the sporangium thereupon thickens, and encloses a mass of green 

 granules ; finally, this sporangium becomes detached from the mother-plant, and 

 sinks into the mud, to give birth sooner or later to a fresh individual. 



ONLY aENUS. 

 Vauoheria. 



Some Alffes of the group of Chlorosporets have, as we have just seen, two sorts of spores ; the one 

 germinating immediately, the others sinking into the mud, where they remain buried during a longer or 

 shorter time before germinating ; these spores are clothed in a tolerably thick membrane, and resemble 

 the Infusorial animals termed Enhystee. The strangest phenomenon is that of Hydrodictyon, where the 

 green matter is concentrated within a joint, and becomes converted into motile corpuscules, which 

 arrange themselves within the tub^ so as to form a complete network, at the same time that other 

 corpuscules escape, and form large germs with a much slower development, named chroniospores, usually 

 5I5 to ^5 of an inch in diameter ; these increase for some time in size, then give birth to other cor- 

 puscules furnished with vibrating hairs, which develop into a new individual in the form of a net 

 (Sydrodictyon, Coloeoehcete, &c.). During their torpid state these chroniospores resemble a Protococcus 

 of jij in. in diameter, and have often been described as very different species from their parents. 

 The knowledge of these curious phenomena is due to MM. Pringsheim and Hofmeister. 



8 A PBOLEGNIE^.—MTGOPUTGEJE, Kutzing. 



Colourless aquatic filamentous Algm (?), resembling Vaucheria in structure, 

 growing on decomposing organic matter, presenting rounded motile zoospores, fur- 

 nished with hairs, resembling the spores of Gonfervce or Vaucheria ; and also sporangia 



containing spherical oogonia. 



GENEEA. 



Saprolegnia. Achlya. Pythium. 



These singular vegetables are considered to be Fungi by some botanists; they live, in fact, on organic 

 matters in a state of decomposition in water, where they act upon oxide of iron by decomposing the carbonic 

 acid, absorbing the oxygen, and thus setting free the sulphuretted hydrogen, which destroys the vegetables 

 or animals near it. Notwithstanding the significance of these biological phenomena, several physiologists 

 who have carefully studied Saprohgnieee do not hesitate to class them amongst Alga. ' Saprolegnia ferax,' 

 savs Thuret, ' is usually found on the bodies of drowned animals, which it covers with a whitish down ; 

 it "even attacks live fish. Nothing is easier than to procure this singular Alga. Let a vase be filled with 

 water from a garden tub, and some flies be thrown into it, and it will usually be developed in a few days. 

 The body of the fly becomes covered with hyaline filaments, which radiate around it, enveloping it with 

 a whitish zone. Under a microscope, these filaments are seen to be continuous, simple or scarcely 

 branched, and to contain minute gi-anules which show a motion resembling that which is seen in the 

 hairs of Phsenogams. These granules are very numerous, especially towards the upper extremity of the 

 tube, to which "they give a grey, somewhat russet tint. This portion soon becomes isolated from the rest 



' I have not adhered literally to the description of this operation in the original, which would not he clear in 

 English.— Ed. 



