102 WAYSIDE AND WOODLAND FERNS. 



external coat is a hard shell, and the interior is divided into 

 four compartments, in each of which a projection {placenta) from 

 one of the walls bears a number of pear-shaped sacs containing 

 spores (Plate 105). Those in the upper part of the compart- 

 ment are filled with microspores. Each of the sacs in the lower 

 portion of the chamber contains a single egg-shaped megaspore, 

 which, however, is several hundred times larger than a micro- 

 spore. The megaspore has a funnel-shaped opening through 

 its outer coat, and through this opening ultimately a prothallium 

 emerges, which is entirely free from chlorophyll, the green 

 colouring matter that is developed in the prothallia of the 

 True Ferns. An archegone develops on the prothallium, but 

 no antherids : these are furnished otherwise. The prothallium 

 of the Pillwort is thus shown to be female only, and not bisexual 

 as in the True Ferns. Each microspore produces an antherozoid, 

 and swarms of antherozoids gather in the funnel-shaped opening 

 of the megaspore, where they find entrance to the archegone 

 and fertilize it. 



The Pillwort grows on the margins of lakes and bogs chiefly, 

 where in winter it is submerged in shallow water, and in summer 

 is merely on moist land ; but it is sometimes found abundantly 

 on land whose surface is dry during a great part of the year and 

 swampy only in winter. Its British range is southward from 

 Skye and Sutherlandshire to Hampshire and Cornwall. In 

 Ireland it is very rare, and found only in the West and the 

 North-east. Its wider range is limited to Europe, and even 

 there it does not extend south of the Alps. 



The popular name Pillwort has obvious reference to the 

 pill-like form and size of the capsules, and the generic name 

 Pilularta is from the Latin pilula, which has the same 

 significance. Alternative popular names are Pepper-grass 

 and Pepper-moss, and it is clear that the original users of 

 these names saw in the capsules a likeness to whole pepper 

 rather than to pills. 



