CHAPTER XIX. 

 BROWN AND RED ALGyC. 



265. If it is desired to extend the study of the alg« to other groups, 

 especially to some of the marine forms, examples of the brown algae and of 

 the red algae may be obtained. These are accessible at the seashore, and 

 for inland laboratories material iliay be preserved in formalin [2^%). 



266 The brown algae (Phaeophycese).* — A good representative of one 

 division of the brown algse and one often used for study is the genun /urns. 



267. Form and occurrence of fuons. — This plant is a more or less 

 branched and flattened thallus or "frond." One of them, illustrated in fig. 

 1 1 9, measures i^—^^ocm (6-12 inches) in length. It is attached to rocks 

 and stones which are more or less exposed at low tide. From the base of the 

 plant are developed several short and more or less branched expansions 

 called "holdfasts," which, as their name implies, are organs of attachment. 

 Some species (F. vesiculosus) have vesicular swellings in the thallus. 



The fruiting portions are somewhat thickened as shown in the figure. 

 Within these portions are numerous oval cavities opening by a circular pore, 

 which gives a punctate appearance to these fruiting cushions. Tufts of hairs 

 frequently project through them. 



268. Structure of the conceptacles. — On making sections of the fruiting 

 portions one finds the walls of the cavities covered with outgrowths. Some 

 of these are short branches which bear a large rounded terminal sac, the 

 oogonium, at maturity containing eight egg cells. More slender and much 

 branched threads bear narrowly oval antheridia. In these are developed 

 several two-ciliated spermatozoids. 



269. Tertilization. — At maturity the spermatozoids and egg cells float out- 

 side of the oval cavities where fertilization takes place. The spermatozoid 

 sinks into the protoplasm of the egg cell, makes its way to the nucleus of 

 the egg, and fuses with it as shown in fig. 125. The fertilized egg then 

 grows into a new plant. Nearly all the brown algse are marine. 



* The members of the group possess chlorophyll, but it is obscured by a 

 brown pigment. 



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