HIDDEN MARRIAGES 



561 



Photo by] 



FIG. 708. Halymenia Ugulata. 



A handsome Red Seaweed. The lobes of the variously divided fronds bear many shoots or branche 



[E. Step. 



from lateral sporangia. There are bodies known as gametes formed in 

 gametangia, which resemble the asexual swarm-spores, but which join in 

 pairs, and, as a result of their fusion, give rise to zygotes, from which new 

 plants develop. There are flask-shaped depressions (conceptacles) in the 

 surface of the thallus, within which are produced antherids and oogones. 

 the former discharging motile spermatozoids, and the latter oospheres. 

 In most species the conceptacle is male or female ; in Fucus platycarpus 

 both antherids and oogones are produced in the same conceptacle. Several 

 species of Fucus are the most abundant seaweeds on our coasts, par- 

 ticularly where there are rocks. Fucus serratus (fig. 702), and Fucus 

 vesiculosus drape all the reefs and afford valuable cover for innumerable 

 marine animals. 



The CHLOROPHYCE.E, or Green Algae, are of much simpler structure than 

 the foregoing : many of them consist of a single cell, and some of these, 

 owing to their active motile powers, were formerly considered as low forms 

 of animal life. The methods of reproduction are varied, and sexual union 

 is not general. In the Order Protococcoidese all the species are unicellular, 

 though in some there is a loose union of a few or many individuals into a 

 colony that may give them the appearance of being multicellular. Some of 

 these are found in all stagnant water and on wet walls and tree-trunks, 

 multiplying by simple division of the cell, or by the breaking up of the 

 protoplasm into a number of swarm-spores, each provided with a couple of 

 cilia. These are set free by the rupture of the cell-wall. The Algae already 



n18 



