Ii8 THE BOOK OF NATURE STUDY 



by the wind. When this has happened the stalk has become 

 weak and limp, and soon it falls over and perishes. It is a fragile 

 and temporary structure, serving only to hold the capsule well 

 up in the air, above the thallus, until the spores have been shed. 

 This is true of liverworts generally, the delicate and short-lived 

 fruit contrasting strongly with the stiff stalk and more highly 

 organised capsule of the mosses. If you do not happen to ex- 

 amine a patch of Pellia at the right time (during the first few 

 months of the year) you will see nothing of its fruits. The sperm 

 pockets are produced in small cavities on the upper side of the 

 thallus, which are often very conspicuous through being raised 

 and wart-like. 



Another very conspicuous liverwort, which you are almost 

 certain to find in the same habitats as Pellia, and often growing 

 mixed with it on stream banks, is Fegatella conica, a large plant 

 for a liverwort. The thallus is brighter green than that of Pellia, 

 and may be six inches or more in length, and over half an inch 

 broad. It branches in the same way as Pellia by repeated 

 forking at the growing ends, but differs markedly in that the 

 upper surface shows a network of fine lines. At the centre of 

 each of the diamond-shaped areas thus marked out there is a 

 white spot. Each of these spots is an opening in the roof of 

 an air-chamber, as is easily proved by dipping the plant into hot 

 water ; an air-bubble escapes from each pore. The air-chambers 

 are arranged in a layer, their side walls corresponding to the 

 lines seen on the thallus. In autumn and winter the plants often 

 bear, at the front of each branch, conical bodies resembling small 

 pointed toadstools, and in spring each of these bodies is raised 

 to a height of two or three inches by the rapid elongation of its 

 stalk. These bodies are not single fruits like those of Pellia, 

 however. Each has six lobes at its edge, and from each lobe a 

 small black capsule projects a little distance, hanging downwards. 

 The whole structure is a special branch of the thallus, which 

 grows up into the air and carries with it six fruits. The individual 

 fruits have, of course, no need for long stalks ; they have stalks, 

 but these are short just long enough to push the capsule down 

 beyond the lower surface of the cone, and so expose the spores 

 to the wind. The sperm pockets are also collected into groups, 



