CRYPTOGAMS 325 



Each antheridium gives rise either to one or, as is more generally the case, to two 



spermatozoids. The spermatozoids are smaller than the asexual swarm - spores, 



but have a similar circlet of cilia. They penetrate the opening in the oogonium 



and fuse with the egg -cell, which then becomes 



transformed into a large, firm-walled oospore. On 



the germination of the oospore its contents become 



divided into four swarm-spores, each of which gives 



rise to a new cell filament. In the adjoining figure 



(Fig. 246) a germinating oospore of Bulbochaete 



with four swarm-spores is represented. 



In some species of Oedogouium the process of 

 sexual reproduction is more complicated, and the 

 spermatozoids are produced in so-called dwarf 

 males. These are short filaments (Fig. 245, 0, a) 

 consisting of but few cells, and are developed from Fig. 246. — Bulbochaete intermedia. 

 asexual swarm-spores (ANDROSPORES) which, after ^.Oospore; B, formation of four 

 swarming, attach themselves to the female fila- swarm-spores in the germinating 

 ° , T nl oospore. (After Pringsheim, x 



ments, or even to the oogonia. in the upper cells 2 50 ) 



of the dwarf-male filaments thus derived from the 



androspores, spermatozoids are produced which are set free by the opening of a 

 cap-like lid (Fig. 245, D, a). In consequence of the greater complication in the 

 process of their sexual reproduction, the oogamous Confervoideae are considered to 

 represent a higher stage of development than the isogamous forms. 



Order 3. Siphoneae 



The Siphoneae are distinguished not only from the Chlorophyceae 

 but from all other Algae by the structure of their thallus, which, 

 although more or less profusely branched, is usually composed of but 

 one cell, or if it is multicellular, each cell contains several nuclei. In 

 the first case, the cell wall encloses a single protoplasmic mass, in the 

 peripheral portions of which are embedded the many nuclei and numerous 

 small green chromatophores. In the class of the Hyphomycetes, the 

 Phycomycetes, or Algal Fungi, exhibit the same characteristic structure, 

 and may be regarded as probably derived from the Siphoneae. 



The Siphoneae comprise about forty genera, which, however, do not 

 include a great number of species. They live for the most part in 

 salt-water, although the species of FaucJieria thrive in fresh-water or 

 are found as terrestrial Algae, growing on damp soil. Botrydium is 

 also terrestrial, while some forms of the Siplwneae are endophytic, and 

 live in the leaves of the higher plants. 



Sexual reproduction has advanced to oogamy only in the genus 

 Vaucheria ; in other instances it is isogamous and the conjugating 

 gametes are alike in form and size. 



The simplest form of the Siphoneae is represented by Botrydium, to which genus 

 belongs the cosmopolitan species Botrydium granulatum. This Alga grows on 

 damp clayey soil, where it forms groups of green, balloon-shaped vesicles about two 

 millimetres in breadth. The vesicles are attached to the ground by prolongations 

 from the base, in the form of a branching system of filamentous rhizoids devoid of 



