94 BRITISH TERNS. 



like head. The organs of reproduction at once distinguish 

 the Club-mosses from all other plants. 



The family group of the Club-mosses consists of two 

 genera, or less comprehensive family groups, which are 

 technically called Lycopodium and Selaginetla. The true 

 Lycopodiums are known by having kidney-shaped spore- 

 cases, containing minute powdery or granular spores ; these 

 have been called antheridia. In the Selaginellas, an addi- 

 tional kind of spore-case is produced, which contains three 

 or four roundish fleshy spores, many times as large as the 

 granular spores just mentioned, and marked at the apex by 

 three elevated ridges ; these larger bodies are called oopho- 

 ridia. The true explanation of these parts is a matter of 

 doubt ; all that seems certainly known being, that the larger 

 spores or oophoridia, germinate, or at least vegetate. It has 

 been usual to regard both sets of organs, when present, as 

 axillary to the leaves or bracts, and so they may be considered 

 for all practical purposes ; but a different theoretical expla- 

 nation has been given of them. 



These plants, like the Ferns, are most abundant in hot, 

 humid, and especially insular situations in the tropics, be- 

 coming scarcer northwards, but often even in very northerly 

 regions covering large tracts of land. Our native species, 

 with one exception, are found most abundantly on the high 

 lands of the north, decreasing in quantity as they advance 

 southwards. Many of the tropical Club-mosses and Sela- 

 ginellas are extremely beautiful : some are of scandent 

 nabit, and many of them attain considerable size. 



Though of humble growth, and altogether unattractive in 

 appearance, the Club-mosses are not without their use. 

 More than one species is used in dyeing operations, and 

 several have a medicinal reputation. The powdery spores, 

 often called pollen, produced in considerable quantities by 

 one common species, are highly inflammable, and used in 

 pyrotechny under the name of vegetable brimstone. Being 

 of a drying and healing nature, this ' pollen' is also used to 

 prevent excoriation ; and in pharmacy is used sometimes for 

 coating pills, as it is with difficulty wetted. The Common 

 Club-moss is emetic, and the Fir Club-moss is a cathartic and 

 a powerful irritant ; the former is used in the treatment of 

 cutaneous disorders, and is a reputed remedy for a dreadful 

 disease called Plica Polonica. 



The species of Club-mosses now existing have been 

 thought to be the direct representatives of the great tree- 

 like Lepidodendra of a former age met with in a fossil state, 



