In 1878 Mul l e r of Denmark recognized two types of humus formation in forest soils and named these "mull" and "mor" 14 The mull type of humus has a loose, friable, crumbly structure; the organic matter is weil mixed with the mineral soil and plant residues can no longer be distinguished. In the case of the mor type of humus, plant residues can still be recognized and organic marter remains on the surface of the mineral soil 14. Soils developed under a well-drained mor have a podzol profile whereas soils under a welldrained mull have a brown earth profile 12 Different opinions exist concerning factors affecting development of mull and mor. According to H a n d l e y 6 many investigators regard vegetation as an important factor. The mull type is usually found under deciduous litter, whereas the mor type is usually found under coniferous litter. The reasons for this are not weil established, although it is believed that difference in the chemical composition of the litter may be partly responsible. B r o a d f o o t and P i e r r e 2 believe that the over-riding factor governing the type of humus produced is the rate of decomposition of the litter, depending largely upon the inorganic fraction of the dead leaves. Many workers have concluded that climate exerts a primary control, more particularly in the case of mor, where low temperatures