and sometimes as few as two. In young conceptacles larger numbers of developing oogonia are seen, so possibly space considerations prevent their reaching maturity. Oogonium Development and Maturation The oogonia and the sterile hairs which separate them are at first indistinguishable, as both arise as papillae from the lining layer of the conceptacle. Soon the oogania can be distinguished by their more densely staining contents. The fully developed oogonia of C. elongatum, C. maschalocarpum and C. plumosum reach a length of about 142μ with a maximum diameter of 123μ in the first two species and 95μ in C. plumosum. After their liberation the oospheres become spherical with a diameter of up to 160μ in the two latter species, though C. plumosum tends to be rather smaller. A comparable measurement for extruded C. elongatum oospheres could not be obtained. The “almost mature oogonia” of C. elongatum Text-Fig. 1.—A. B. C—Early stages of conceptacle development in C. plumosum var. capillifolium. A—Still within the apical groove and showing the formation of the tongue cell. B and C—Slightly order stages showing the concurrent development of the oogonia and the concrescent hairs. Scale = × 435. D—Section of an almost mature conceptacle of C. maschalocarpum which contained 4 oogonia, showing the large oogonia and central tuft of hairs. Scale = × 285. All outlines drawn with the aid of a camera lucida.