RHODOPHYCEAE 



body, puts out a tube through which the embryonic cells are conveyed to 

 a neighbouring cell, called an auxiliary cell, in which the further 

 development is completed. The auxiliary cell then forms a number of short 

 tubes each of which produces one or more spores, the carpOSporeS-, the 

 whole structure produced by the auxiliary cell being called the cystocarp. 

 Several groups of cells, each containing one fertile carpogonial branch and 

 one auxiliary cell, are found in each conceptacle, which therefore subsequently 

 contains a corresponding number of cystocarps"". 



As a second example of the Red Algae the genus Gelidium may be 

 mentioned (Plate 2, Fig. K). This represents the 

 commonest type of plant body (thallus) met with 

 among Red Algae, namely one which is freely 

 branched, the branches being rather slender and 

 somewhat leathery in texture. The tetraspores of 

 Gelidium are arranged in cruciate form. The sexual 

 reproductive organs are similar to those of Cheilo- 

 sporum, but are not sunk in special conceptacles as 

 they are in that genus. The carpogonium is found 

 just below the surface of the thallus, surrounded 

 by a number of auxiliary cells, the trichogyne pro- 

 jecting on the outside through a small opening in 

 the surface of the thallus. After fertilisation the 

 embryonic cells, unlike those of Cheilosporum, develop 

 in the carpogonium ; but when the spore-bearing 

 tubes are produced, each becomes joined to an 

 auxiliary cell before producing a spore. The cysto- 

 carp is shown in Fig. 15. 



Fig. 15. Gelidium car til a- 

 gineum. (L.) Gaill. 

 1. Habit of a pinnule. 

 2/1. 2. Longitu- 

 dinal section through 

 a bilateral, terminal 

 cystocarp. 45/i- 



(After Schmitz) 



* In such cases the whole conceptacle with its contents is generally called the 

 cystocarp. 



3— 2 



