446 SYSTEMATIC BOTANY. 



connected cortical filaments. The five spiral cells terminate at the summit 

 in five (or ten) teeth ; and it appears that these teeth separate from each 

 other at a certain epoch, leaving a free passage down the centre to the 

 wall of the central celt. In this state we may compare the structure to 



Fig. 509. 



"Nilella flexiKs. A, manubrium of segment of globule, with numerous filaments in which 

 the antherozoids are developed; B, portion of filament, very highly magnified; C, anthe- 

 rozoids. 



an archegonium, or to an ovule of Phanerogamia. The spermatozoids 

 from the globule pass into the canal between the crown of teeth of the 

 nucule, and cause it to become fertile. The product, however, of the 

 fertilized central cell is not a free embryo or a spore, but it becomes itself 

 the first cell of the new plant, like a spore. After fertilization the nucule 

 drops off from the parent, passes through a stage of rest, and in the 

 following season germinates like a seed or spore and grows up at once 

 into a new plant. Pringsheim, however, states that the spore develops 

 a true prothallus like that of the Mosses.' 



Distribution, &c. The Characese grow in stagnant water, and many of 

 them acquire a dull aspect and brittle texture by becoming encrusted 

 with carbonate of lime, apparently precipitated from calcareous matter in 

 the water, since it is often deficient in cultivated specimens. The un- 

 encrusted kinds, the simple tubes of Niiella, and the young shoots 

 generally are well known as objects displaying in a beautiful manner the 

 rotation of the cell-sap, which takes place throughout these plants. The 

 abundant protoplasmic cell-contents cause these plants to give off a very 

 offensive odour when decaying. The species occur all over the world, 

 most commonly in temperate climates. They have no known uses, and 

 are regarded as noxious from their smell when undergoing decomposition. 



EHODOSPERME^E on FLOEIDE^E. BED SEAWEEDS. 



Class Algae, Endl. Att. Algales, Lindl. 



Diagnosis (Fig. 510.) Marine Algae, mostly of a reel-purple, 

 rarely olive or brownish colour, with a thallus either foliaceous or 

 of branched filaments, sometimes encrusted with carbonate of lime. 



