GROWTH AND REPRODUCTIVE CYCLE OF PLEUROZIUM SCHREBERI (BRID) MITT

The reproductive cycle of the moss Pleurozium schreberi has been investigated by scoring over 600 specimens from Britain and elsewhere, and through regular observations on several populations. P. schreberi is at least functionally dioecious and the stems are perennial, producing all the inflorescences of a given cycle during the autumn. On male plants perigonia develop in large numbers, principally on lateral branches. Relatively few perichaetia are formed on female stems where they are largely confined to the main axes. In Britain perigonial development begins in August, the antheridia remaining in the immature stage during the winter resting phase. Young perichaetia are first recorded in October and the archegonia overwinter in the juvenile stage. Rapid gametangial development takes place in spring prior to the main fertilization period in April and May. Young sporophytes are present from May onwards. Setal elongation is delayed until August, but the late operculum intact stage is reached by October. In Britain the spores are shed between January and April, nine to twelve months after fertilization. Data from the literature and from French, Finnish, and North American specimens suggests a similar cycle in other areas, though with slight differences, notably that fertilization in parts of Scandinavia may be delayed compared with Britain.The results from periodic measurements of marked plants and other techniques suggest that in Britain vegetative growth may also show a winter resting phase, stem elongation being recorded only from April to November. © 1969 OXFORD UNIVERSITY PRESS.