172 



A TEXTBOOK OF THEORETICAL BOTANY 



SPERMATIUM 



Fig. 163. — Ceratniiini riibrum. Formation of antheridia and spermatia from 

 mother cell. {Modified from Gritbh.) 



The Carpogonium 



The procarp originates very close to the apex itself. One of the segments 

 cut off by the apical cell divides to form a group of pericentral cells. The 

 first of these to be formed is the initial of the procarp branch. It elongates 

 laterally and becomes the basal cell. This cell cuts off a four-celled procarp 

 branch, the terminal cell of which is the carpogonium. In Ceramium rubrum, 

 unlike other species of Ceramium, only one procarp is cut off, either to right 

 or left of the basal cell ; in others two procarp branches are formed. The 

 carpogonium elongates and forms a tubular trichogyne at its distal end 

 (Fig. 164). After fertilization the basal cell cuts oft' on the opposite side to 

 the procarp branch a large auxiliary cell. The zygote nucleus from the 

 carpogonium passes into this and the cell then begins to cut off a series of 

 short gonimoblast filaments, from the tips of which carpospores are 

 formed (Fig. 165). These filaments are often simply short lobes of the 

 auxiliary cell. The carpospores germinate to produce the tetrasporic plants. 



Asexual Reproduction 



The tetrasporic plants do not differ morphologically from the sexual 

 ones. The tetrasporangia arise in the cortical cells in the region of the 

 nodes. The details of the division have not been fully investigated, but it 

 appears probable that they are formed by the division of certain of the 

 pericentral cells in the nodal region, which each cut off externally a single 



