234 Plants and their Ways in South Africa 



Adiantum, the Maiden Hair, may be known by the slender, 

 black leafstalks and the fan-like veining. The sori are on the 

 margins of the fronds, and the recurved edge of the frond 

 forms an indusium. The sori are not continuous, as in Pteris. 

 Selaginella belonging to the group Lycopodinece. (Club 

 mosses) is frequently seen in greenhouses. Several species are 



native to South Africa. At 

 the tips of the branches 

 sporangia are clustered to 

 form a cone. In some spor- 

 angia only one of the many 

 spore mother- cells develops, 

 so that when ripe they con- 

 tain only four large spores 

 each (megaspores). Those in 

 which all the spore mother- 

 cells develop contain a large 

 number of small spores (mi- 

 crospores). The megaspores 

 germinate within the spor- 

 angium each forming a pro- 

 thallium much more reduced 

 than that of the fern, in fact 

 the cells barely emerge from 

 the ruptured spore wall, 

 where a few archegonia are 

 formed. The prothallium formed from the microspore is still 

 more reduced and consists of a smgle cell. But one anther- 

 idium is formed which produces several sperm-cells. 



After fertilization, an embryo is developed from the egg- 

 cell which for a time derives its nourishment from the small 

 prothallium. Later, like the fern, it forms roots and becomes 

 an independent plant. 



The life history of the fern may be shown by the diagram 

 below : — 



Fig. 208.— Longitudinal section through 

 a cone of Selaginella. a, macrospor- 

 angium ; d, microsporangium. 



