i8 



RHODOPHYCEAE 



with lime. The branches arc all made up of more or less V -shaped segments, 

 the cells connecting one segment to the next being thicker and stronger than 

 the rest as shown in Fig. \ }. The most frequent method of reproduction is 

 by means of spores which are formed in rows of tour, and are therefore known 

 as tetraspores. This is one of the characteristic methods of reproduction 

 in the Red Algae, though the tetraspores are often arranged in a tetrad 

 instead of in a row. 



In Cheilosporto)!, the tetraspores are formed in flask-shaped cavities in 

 the thallus, called conceptacles, the position of which is shown in Fig. i }, 

 and the structure more clearly in Fig. 14. 



Besides the tetraspores, which constitute a non-sexual means ot repro- 

 duction, there is a characteristic method of sexual reproduction in the Red 

 Algae, unique in the plant kingdom. It has been shown that, in some forms at 

 least, a regular alternation of generations exists in these plants, quite comparable 

 to that met with in the Mosses and Ferns. Although this has not been 

 definitely proved in the case of C/iei/ospontm, it may be assumed that sexual 



Fig. 14. Cheilosporum cultratunu 

 Conceptacle, 75, 1. w. T. s. 



Fig. 13. Chiiloiporum cultratum (Harv.) Aresch. 

 Portion of thallus, 40/1. w. T. s. 



organs are produced by the plants which are formed on germination of the 

 tetraspores, and that tetraspores are produced by the plants which result from 

 germination of the sexually produced spores. It is known that male, female, 

 and tetraspore-bearing plants are distinct from one another. Male and female 

 reproductive cells are each produced in conceptacles similar to those in which 

 the tetraspores are found. The male cells are very small, motionless, spherical 

 bodies, called pollinoids, formed in enormous numbers in each conceptacle. 

 The female reproductive organ is called a carpogoriiwrtt, and is the 

 terminal cell of a short row of cells called the procarp or carpogonial branch. 

 The carpogonium ends in a long hair-like projection called the trichogyne, 

 and to the latter the pollinoids become attached. Fertilisation then takes 

 place, but the fertilised carpogonium, instead of itself developing into the fruit 



