202 TWO PHASES OF PLANT LIFE 



female organ. The wall of the tube at the point of contact is 

 now absorbed and the male gamete passes down the tube and 

 fuses with the female. The gametospore does not germinate 

 and produce a new plant similar to the one that bore the gametes. 

 On the other hand, it produces a number of branches (Fig. 127, 

 B, C), the terminal cells of which develop as spores (Fig. 127, 

 D). These spores on germinating produce the characteristic 

 red algae, which bear tetraspores. The mode of sexual repro- 

 duction outlined above is complicated in the majority of the 

 red algae, owing to the fusion of the germinating gametospore 

 with adjacent cells that contain storage foods. In this way, the 

 formation of a larger number of spores is made possible. Fre- 

 quently a sac-like structure, the cystocarp, is developed about the 

 spores owing to the outgrowths of the adjacent cells (Fig. 128, 

 C). The red algae are of considerable economic importance. 

 Irish moss, Chondriis, is used in the manufacture of jellies, and 

 agar-agar is obtained from several species of algae. Many tons 

 of various kinds of red algae are annually dried and consumed 

 for food in the East. The swallow's nest, of which you have 

 heard so much as an article of food in the Orient, is constructed 

 of algae. 



75. Significant Features in Life History of the Algae. — The 

 germination of the gametospore in the Rhodophyceae is a note- 

 worthy departure in two respects. Unlike previous cases, it is 

 retained on the plant, where it is nourished during its germination 

 and grows practically as a parasite. This relation of the gameto- 

 spore to the mother plant will become more noticeable among 

 the mosses and lead to pronounced changes in the life history of 

 the plant. In the second place, we notice that the gametospore 

 in the red algae produces a number of cells before the spores are 

 formed. In the green and brown algae it either developed di- 

 rectly into a plant similar to the mother plant, as in Spirogyra, 

 Vaucheria and Fucus, or zoospores were first formed which devel- 

 oped into a plant similar to the parent, as in Ulothrix and Oedo- 

 gonium. What is the significance of this variation in the germi- 

 nation of the gametospore? Attention has been directed in the 

 study of Ulothrix, p. 182, to the fact that there are two phases in 



