SIPHONACE^E 563 



spore escapes, not, however, until it has undergone marked changes 

 of form, and exhibited curious movements. Its motions continue 

 for some time after its escape, and are then plainly seen to be due 

 to the action of the cilia, which form a complete fringe round it. 

 If it be placed in water in which some carmine or indigo has been 

 rubbed, the coloured granules are seen to be driven in such a 

 manner as to show that a powerful current is produced by their 

 propulsive action, and a long track is left behind it. When it 

 meets with an obstacle, the ciliary action not being arrested, the 

 zoospore is flattened against the object ; and it may thus be com- 

 pressed, even to the extent of causing its endochrome to be dis- 

 charged. The cilia are best seen when their movements have been 

 retarded or entirely arrested by means of opium, iodine, or other 

 chemical reagents. The motion of the spore continues for about 

 two hours ; but after the lapse of that time it soon comes to an 

 end, and the spore begins to develop itself into a new plant. It has 

 been observed by linger that the escape of the zoospores generally 

 takes place towards 8 A.M. ; to watch this phenomenon, therefore, 

 the plant should be gathered the day before, and its tufts examined 

 early in the morning. The same filament may give off two or three 

 zoospores successively. 



In addition to this mode, there exists also in this humble 

 plant a true process of sexual generation. The branching filaments 

 are often seen to bear at their sides peculiar globular or oval 

 capsular protuberances, sometimes separated by the interposition of 

 a stalk, which are filled with dark endochrome ; and from these, 

 after a time, new plants arise. In the neighbourhood of these 

 bodies are found, in most species, certain other projections, which, 

 from being usually pointed and somewhat curved, have been named 

 ' horns ' (fig. 426, A, a) ; and these have been shown by Pringsheim 

 to be antherids, which produce antherozoids in their interior ; whilst 

 the capsule-like bodies (A, 6) are oogones or a/rckegones, each con- 

 taining a mass of endochrome which constitutes an oosphere that is 

 destined to become, when fertilised, the original cell of a new 

 generation. The antherozoids (B, c, d), when set free from the 

 antherid a, swarm about the oogone b, and, attracted by a drop of 

 mucilage formed at the mouth of the oogone, enter it, one or more 

 antherozoids becoming absorbed into the substance of the oosphere. 

 This hitherto naked mass of protoplasm now becomes invested by 

 an envelope of cellulose (C, b), which increases in thickness and 

 strength, until it has acquired such a density as enables it to afford 

 a firm protection to its contents. While in Vaucheria the separate 

 filaments are so slender as to be scarcely discernible to the naked 

 eye, the frond of other genera of Siphonaceae, mostly natives of 

 shallow seas in the warmer parts of the globe, attains very large 

 dimensions. Thus in C odium it is a spongy spherical or cylindrical 

 floating mass, as much as a foot in length ; in Caulerpa it has the 

 appearance of a branched leaf springing from a stem, which puts 

 out roots from its under side ; in Acetabularia it takes a mushroom- 

 like form with a cap or ' pileus,' a quarter of an inch in diameter, 

 divided into regular chambers, at the summit of a cylindrical stalk, 



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