382 ORGANOGRAPHY. 



as in Vaucheria, the spores are ciliated all over ( fig. 32). They 

 may be produced either singly in the cells, as in Vaucheria {fig. 

 833), or in great numbers, as in Achlya; and they ultimately 

 escape by rupturing the coats of the cell in which they are con- 

 tained {fig. 833, g). Some Confervoids have two kinds of 

 zoospores, which are termed respectively macrogonidia and micro- 

 gonidia ; the latter are smaller and longer than the former. 



These zoospores are sometimes confounded with spermatozoids, 

 from which structures, however, they are quite distinct. Henfrey 

 has thus distinguished them : — " The essential character of a 

 zoospore is, that when separated from the parent it becomes en- 

 cysted, and at once developed into a new individual resembling 

 the parent (certain obscure exceptions however occur, where the 

 zoospore, after germinating, at once discharges new ciliated bodies 

 [zoospores or spermatozoids?]). Spermatozoids are transitory 

 structures ; when discharged from the parent-cell they either 

 make their way to a germ-cell of a spore, fertihze it and dis- 

 appear ; or if debarred from this, at once perish without ger- 

 mination." 



Besides the above-mentioned reproductive organs, there have 

 been found in certain genera of this sub-order — sporangia, in 

 which resting-spores are produced by impregnation from anthero- 

 zoids derived from antkeridia. 



2. Rhodosporece, Floridece, or Rose-coloured Algm. — There ap- 

 pear to be three forms of reproductive structure in plants of this 

 sub-order of Algse ; these are termed respectively 1. tetraspores ; 

 2. spores ; and 3. antkeridia. The tetraspore is a peculiar feature 

 of the plants of this sub-order, and at once distinguishes them 

 from their allies. The sexual nature of these Algse would appear 

 to be tolerably well ascertained. 



1. Tetraspores. — These are either naked, as in Callithamnion, 

 and then either situated on the outside of the frond, or more fre- 

 quently collected in masses and immersed in its substance {fig. 

 834) ; or they are collected together in distinct organs of varying 

 forms, called conceptacles {fig. 835), and stichidia {fig. 836). 

 The tetraspore consists of a more or less globular transparent 

 sac or cell, called the perispore, which when mature contains 

 within it four (or rarely three) sporules {fig. 834). The tetra- 

 spores are regarded by some authors as analogous to gonidia, 

 that is — as gemma ; but others consider them as true generative 

 spores, and regard the spores as gemmse. 



2. The Spores, like the tetraspores, vary in their situation. 

 Sometimes they are collected together in masses without any 

 special sac ; but generally they are situated in distinct hollow 

 conceptacles, which have received different names, according to 

 their structure and arrangement : the terms favelles {fig. 837), 

 ceramidium {fig. 838), and coccidiiim are those which are most in 

 use. The spores are generally formed by the transformation of 



