Pilularia
(from pilula, a little ball or pill; alluding to the shape of the heads containing the reproductive organs). Pillwort. ORD. Marsileaceae. A small genus (three species) of obscure little aquatic plants, inhabiting temperate Europe, Western Asia, Australia, and North America. Rootstock creeping under water. Leaves solitary, erect, setaceous. "Capsule globose, two to four-celled, two to four-valved at the top; cells each with a longitudinal, parietal placenta, on which are inserted many pyriform, membranous sacs; sacs in the upper part of the cell full of microspores immersed in mucilage; those in the lower part contain each one macrospore. Microspores globular, full of antherozoids. Macrospores ovoid, with an outer coat of prismatic cells, pierced by a funnel-shaped opening, through which an inner, glassy coat finally protrudes. In germination, a prothallus is developed at the top of the protruded portion of the inner coat of the macrospore, which bursts and frees it. After expulsion, an archegonium is formed on the prothallus, and fertilisation takes place by the contents of the microspore" (Hooker). P. globulifera is found in damp meadows, among grass, especially where they have been overflowed with water during winter; it is widely distributed over England and Scotland, but very rare in Ireland. It is of more botanical than horticultural interest.
P. globulifera (globule-bearing). rootstock slender, often creeping to a considerable length, and rooting at every node. l. bright green, varying from 1in. to 4in. in length. Capsules pill-like, about 1/6in. in diameter, covered with short hairs. h. 3in. (F. D. ii. 223.)