226 



MANUAL OF BOTANY 



plants, at the other end of the scale. It is always naked, never 

 having a cell-vi'all apart from that of the cell in which it is 

 formed (fig. 489). 



The female gamete does not show so much variation. Its 

 typical form is that of an ovoid or spherical mass of protoplasm, 

 withoiit cell-wall or cilia, and it is termed an oospliere. It may 

 escape from the gametophyte, as in Fucus {figs. 495 and 496), or 

 it may remain where it is formed, and become fused there with 





V 



Fig. 489. A. Branched mycelium of Cystopits with youug oogouia, 0[/, og. 

 B. Portion of mycelium bearing oogonium, og, with the oosphere, os ; and 

 antheridium or poUinodinm, an. c. Mature oogonium, with os, the 

 oospore, n. Mature oospore. E, F. Formation of swarm-spores or zoo- 

 spores, 13, from the oospores, i, i. Protruded eudospore. After De Bary. 



the male gamete, which reaches it in various ways, as will be 

 described later. In the Red Seaweeds it is not differentiated 

 at any time. 



The process of coalescence of differentiated dissimilar gametes 

 is known as fertilisation, and the product is termed an oospore 

 or zygote. It immediately clothes itself with a cell- wall. The 

 terin fertilisation is also appHed to the process in the lied 

 Seaweeds,, although no differentiated zygote results. 



