128 PLANT LIFE. 



The remaining type of structure which can be noticed at 

 present may again be described as a modification of the 

 Batrachospermum plan, which, it will be remembered, con- 

 sists of a monosiphonous axis, producing distinct and 

 scattered whorls of branches. If a vertical section of a branch 

 of Gloiosiphonia capillaris be examined, it will be found to 

 agree in all essential points with that of Batrachospermum, 

 the only point of diiference being that in Gloiosiphonia 

 the secondary branchlets of the whorls branch repeatedly in 

 a forked or dichotomous manner, and consequently become 

 so widely extended that the branches of contiguous whorls 

 meet, so that instead of the moniliform or beaded appearance 

 presented by a branch of Batrachospermum, due to the 

 scattered whorls, we get a continuous cylindrical branch 

 in Gloiosiphonia, brought about by confluence of the whorls, 

 and as the ultimate cells of the branches are very small and 

 held together by mucilage, the periphery of the branch is 

 the most compact part, of the structure. So long as the 

 branches are equally developed on every side, a circular or 

 cylindrical thallus results. When the branches become 

 more developed in one direction than in another, which 

 usually takes place on opposite sides of the axial row, a 

 flattened thallus is formed. 



The presence of lime encrusting the species of Melobesia 

 has already been noticed, and the same peculiarity is highly 

 developed in the genus Corallina and its allies, which in 

 addition closely resemble in habit some of the smaller 

 corals, hence our common species of Corallina are 

 popularly known as corals, and in like manner several 

 members of the Animal Kingdom, as species of Flustra 

 or " sea-mats," are popularly considered as seaweeds. 



The asexual mode of reproduction by tetraspores is on 



