278 PLANT LIFE. 



very large numbers and are not of much interest except 

 from the geological standpoint 



The Clubmosses {Lycopodia) are generally creeping 

 plants with upright spore-bearing and other branches. 

 The spores are contained in small sporangia, placed 

 above the leaves. The spores produce an underground 

 tuber-like protJiallium on which the antheridia and 

 archegonia occur. The fertilised egg-cell of the 

 archegonium produces a new Lycopodium. 



A Selaginella is very like a Lycopodium in appearance 

 but differs from it in having the spores differentiated into 

 male, or microspores^ and female, or macrospores. The 

 sporangia open in two valves ; the female spores, of which 

 there are only four, are jerked or thrown off by a pecu- 

 liar elastic contraction of these valves and one at a 

 time. The male spores, which are rather numerous, are 

 also thrown off in a similar manner. 



During the coal-measures, Club-mosses were gigantic 

 trees. Such a form as Lepidodendron must have been 

 very like a specimen of Lycopodium Selago magnified 

 to the height of 50-70 feet and a forest of such Club- 

 moss trees must have had a most peculiar appearance. 



The Horsetails {Equisetaceae) differ altogether from 

 the rest of the Fern-alliance. They have long under- 

 ground or under-water rhizomes, from which rise the 

 erect stems. The leaves are very small and are placed 

 in circles along the stems. From each leaf circle a 

 whorl of elegant drooping branches is produced. The 

 main stem is generally surmounted by a close-set spiral 

 of spore leaves. In some species, however, certain 

 stems are barren and carry many green branches, whilst 

 the spore-producing stems are not branched, and are 

 formed before the others. The Horsetails are found in 

 quite a variety of situations. Some, such as E. arvense^ 



