The subject of this memoir did not leave any personal record with the Royal Society, but I have been fortunate in having the assistance of his niece, Mrs Margaret E. Franklin; Professor T. B. L. Webster, who was a close friend for the last 25 years of W. H. Lang’s life; the late Lord Stopford, who was also a close friend and was Vice-Chancellor of Manchester University during the last seven years of Lang’s tenure of the Chair of Cryptogamic Botany, and Professor Wardlaw, who succeeded to that Chair when Lang retired. To all these I wish to acknowledge my indebtedness for their unstinted help which was the more valuable since Lang was not one who talked about himself and, indeed, was rather uncommunicative about his private life. W. H. Lang’s father was Thomas Bisland Lang, the son of William and Joan Lang who were married in 1825 and lived at Bridge-of-Weir, Renfrewshire. This couple had a typically large nineteenth century family of eleven children of whom Thomas Bisland was the youngest but one. A brother and a sister died in infancy, as was so frequent at that epoch, but Thomas’s sister Margaret lived to the age of 89 whilst his sister Mary lived to be 80, which, despite the fact that all but one of William Henry’s brothers died before they were 30, indicated that the stock was not potentially deficient in physical stamina. Nevertheless Thomas himself died at the age of 34, only two years after the birth of William Henry. The Baptismal Register records that our subject was born on 12 May 1874 at Withyham, Groombridge, Sussex. It was to this place that William’s father had come as a doctor with his young wife to establish a medical practice. After the untimely death of his father, the young baby and his mother returned to live at Bridge-of-Weir. Thus William was brought up in what must then, nearly 90 years ago, have been quite rural conditions for, even to-day, Bridge-of-Weir has a population of only just over 3000 inhabitants. The nearest city to their home was Glasgow, 14 miles away, a long distance when the only alternative to walking was a horse-drawn conveyance, since bicycles were a rarity till the close of the century.