242 PHARMACEUTICAL BOTANY 



Upon the maturation of the antheridium the sperms are liberated 

 into the water, and, propelled by their cilia, find their way to the 

 oogonia which they enter, the one best adapted fusing with the egg 

 in each case and fertilizing it. The resultant cell is cafled the 

 oospore. This undergoes a resting stage and later germinates as a 

 proembryo. The proembryo consists of a simple filament and a 

 long rhizoidal cell. From this proembryo, the adult stern arises as a 

 side branch. 



CLASS II. PHAEOPHYCE^E, THE BROWN ALG^E 



Mostly marine forms showing great diversity in the form of their 

 vegetative bodies. They occur for the most part in salt water be- 

 tween the high and low tide marks. Their bodies are usually fixed 

 to some support in the water by means of a holdfast, and are often 

 highly differentiated both as to form and tissues. Some reach 

 hundreds of feet in length as, for example, Macrocystis which grows 

 in the Pacific Ocean off the coast of California. They all contain 

 the brown pigment called phycophcein and the green pigment, chloro- 

 phyll both of which are present in their chromatophores. A yel- 

 lowish pigment called phycoxanthin has also been isolated from some 

 of the species. Many of the kelps and rockweeds belonging to this 

 class have long been sources of iodine, potash and sodium. 



A Filamentous Brown Alga, Ectocarpus Siliculosus. Ecto- 

 carpus occurs as tufts of branching filaments, each of which is 

 many-celled. These tufts are found on eelgrass or other algae as 

 well as attached to pilings of wharves in salt water. It is a striking 

 illustration of the simplest form of brown algae and serves to show 

 the beginning of a more complex form of reproduction than that 

 observed in the forms studied up to this time. On examination of a 

 filament we find it to consist of many cells joined end to end. A 

 single cell has a cell wall of cellulose. Just within the cell wall 

 there is a layer of protoplasm. Going toward the center we find an 

 irregular chromatophore containing a brown pigment called phyco- 

 phaein. From certain cells of the filament spherical sporangia (spore 

 cases) arise, which are unicellular. They contain numerous biciliate 

 zoospores, which escape into the sea water, move about and later 



