GENERAL MORPHOLOGY OF PLANTS 



FILAMENTOUS GREEN ALG.E. 



The Confervas (Confervoidece). 



376. General characters. The larger number of these algae 

 are thread-like, either simple or branched. Some of the marine 

 forms are leaf -like, as the "sea lettuce." The chlorophyll is 

 in small, oval, flattened chloroplasts. They multiply by the for- 

 mation of special bodies from the protoplasm of individual cells. 

 These bodies are called spores, and are provided with cilia so 

 that they swim about in the water after escaping from the parent 

 cell. They are thus called "swimming spores," "Zoospores," 

 or " Zo&gonidia." These spores are not formed as the result 

 of a sexual process. The process is an asexual one, hence they 



are often termed asexual 

 swimming spores. Sexual 

 reproduction takes place 

 in some by the fusion of 

 two swimming gametes 

 (spores) similar to the 

 asexual spores, forming a 

 zygospore. Jn others defi- 

 nite sexual organs are 

 formed, a large one, the 

 female organ, an egg case 

 (called an oogonium) , 

 which contains the egg (or 

 oospore); and a smaller 

 one, the male organ, a 



sperm case (called an 

 antheridium) y containing a 

 the sperms. Fertilization 



E 



Fig. 185. 



Ulothrix zonata. A, base of thread. B, cells with 

 zoospores, C, one cell with zoospores escaping, 

 another cell with small biciliate gametes escaping 

 and some fusing to form zygospores; , zoospores 

 germinating and forming threads; F, G, zygospore 

 growing and forming zoospores. (After Caldwell 

 and Dodel.) 



number of small motile male cells, 



in these results from a fusion of a sperm with the nucleus of 



the egg. 



377. Ulothrix. Ulothrix is an example of the first kind of 

 sexual reproduction described above. The plant forms simple 

 threads. In asexual reproduction a number of small, oval, 4- 



