CRYPTOGAMIC LABORATORY STUDIES 259 



arrangement of the leaves at the summit. The sporogonia are mature 

 later. Preserve in alcohol, if necessary. Other mosses (e.g. Mnium) 

 will serve. The protonerna may be found in greenhouses and on soil 

 where moss is growing. 



390. Fern. Prothallia are easiest got in greenhouses. They may 

 best be grown (by the florist) on potsherds. The smaller prothallia 

 are likely to have antheridia alone. For the spores, use preferably 

 some Aspidium, taken when the sori are youngish. If necessary 

 preserve this material in alcohol. In the Maidenhair Fern the sori 

 are covered by the recurved leaf margin not an indusium. If 

 smallish prothallia, which have not been wet for some time, are placed 

 in a drop of water on a slide, the aniherozoids are likely to be seen ; 

 use a low power of the compound microscope. 



396. Selaginella, from greenhouses, in fruit in early spring (some 

 species at other times). 5. rupestris is found in dry situations (as 

 bare hilltops) at the edge of ledges in poor soil. It looks at a 

 distance like a stiff, coarse moss. 



400. Lycopodium is the " ground pine " used for Christmas decora- 

 tions. In fruit in late summer. 



402. Equisetum arvense is common on railroad banks, the fertile 

 shoots appearing in early May, the vegetative shoots later. 



