Page:The American Cyclopædia (1879) Volume I.djvu/324

 300 ALG^E ALGAROTTI also to give a gloss to silks and to size paper ; windows are frequently made of strips of bam- boo coated with this glue. As objects of beauty this order affords many fine species, as the lau- rencia pinnatifida, shown in the first cut. The characea are aquatic plants of a more obscure organization than any of the previous orders ; they usually exhale a fetid odor, supposed to be unwholesome, and are curious as exhibiting under the microscope a circulation in their transparent stems and branches. Reproduc- tion of the algce. There are four principal ways in which algae may produce new individ- uals. 1. A direct action is exercised by forma- tions playing the part of male organs upon a minute mass of protoplasm, which before this action has no coating of cellulose, but now ac- quires this and becomes a spore. This male organ is analogous to the anther of flowering plants, and is hence called antheridium; but while the anther produces pollen, the antheri- dium gives birth to little bodies of a very dif- ferent nature, which have the power of loco- motion by means of vibratile ciliee and closely resemble animalcules ; these are called anther- ozoids. An example of this method is seen in vaucheria, an alga consisting of green, one- celled filaments, common in ditches. The an- theridium develops from the side of one of these filaments as a horn-like projection, and is soon followed by a similar excrescence* in its immediate neighborhood called the sporangi- um ; these are at first continuous with the tube on which they grow, but finally form a parti- tion completely separating their contents from the parent plant. The antheridium then opens, discharging the antherozoids, which move at once toward the opening end of the sporangi- um, and are met by a layer of mucilage, into which they thrust themselves and then retire, repeating this curious action for half an hour, until a thin membrane appears across the open- ing, due doubtless to the penetration of an an- therozoid ; and then the others move more and more slowly, and at last become quite still. The fecundated sporangium when grown de- taches itself from the plant as a cell filled with brownish particles. After three months it re- covers its green color and elongates into a tubu- lar filament of the perfect alga. 2. The same vaucheria often shows the extremity of its filament swollen into a club shape, and the green matter is condensed there until it as- sumes a blackish tint and becomes enclosed in its own membrane. The end of the filament bursts and permits the escape of a zoospore, which is covered with vibratile cilia having so rapid a motion that to make them visible it is necessary to retard the motion by opium, or arrest it entirely by a very weak solution of iodine. The zocispores, produced apparently without the intervention of sexes, move through the water for some time, and when the cilia cease to vibrate soon germinate. 3. The ordinary fucus presents in its substance javities or conceptacles opening when mature by small pores, through which escape, in the female plants, the sporangia, which contain eight spores in a membrane which soon dis- solves, setting free in the water the spores, and in the male plants the antheridia, which also burst and discharge antherozoids, which are small bodies with two long cilia. The anthero- zoids meet the spores, which seem simply mu- cilaginous globules, and attaching themselves impart to the spores a rapid rotary motion, lasting usually six or eight minutes. The spore immediately becomes covered with a mem- brane, and is ready to germinate as a new fucus. 4. Reproduction by conjugation is seen in the fresh-water alga spirogyra, which is common in stagnant water in the early spring. The slender filaments of which it is composed are divided into cells by transverse partitions, and these cells contain gelatinous endochrome. Two adjacent filaments conjugate on contact, two cells swelling toward each other and final- ly uniting, when the contents of one are trans- ferred to the other, and the communication is closed and the full cell develops a spore. The spores are formed sometimes in one filament, sometimes in the other, and when mature break away the cells and elongate into new spirogyras. This process may be seen with a microscope of low power, and so short is the time occupied that it may be easily followed from beginning to end. Like higher plants, algffl absorb carbonic acid and exhale oxygen in sunlight, although they are not so dependent on the sun for their bright colors, these exist- ing at depths where the light would be less than half a candle. Professor Harvey has adopted a classification from the color of the spores, which is often used as exceedingly con- venient, into chlorosperms, with green spores and usually with a greenish color over all the plant ; rhodosperms, with rose-colored spores ; melanospores, with olive-brown spores. From the motive powers of the zoospores of alga?, it is not strange that the early microscopists should have confounded the animal and vege- table kingdoms, which come so close together in the spores of alga3 and the lowest of animals. ALGARDI, Alessandro, an Italian sculptor, born in Bologna about the year 1600, died in 1654. Doraenichino obtained employment for him at Rome. By a statue of St. Philip Neri in the sacristy of the Oratorian church in that city, and a colossal group representing the decapi- tation of St. Paul in the church of the Barna- bites at Bologna, he achieved a reputation as the first sculptor of his time. He was chosen to execute the bronze statue of Innocent X., erected to commemorate the completion of the capitol at Rome. He produced the monument of Leo XI. in St. Peter's ; and for one of the altars in the same church he made the largest basso-rilievo in the world a work in marble representing Attila checked by St. Leo. ALGAROTTI, Francesco, an Italian scholar, born in Venice, Dec. 11, 1712, died in Leg- horn, March 3, 1764. After studying in Rome