_General Information_: Easily recognised by the dull colours and purple reaction with alkali; there is no British species with which _L. turpis_ can be mistaken. The purple reaction is similar to that found in the familiar school laboratory reagent litmus, for the compound found in _L. turpis_ turns purple in alkali and reddens in acidic solutions. First discovered by Harley in 1893 this reaction marked the beginning of a whole series of chemical studies on the agarics which has led to the discovery of many unique compounds. _Illustrations_: Hvass 214 (but too green); LH 213; NB 113³; WD 38¹. General notes on the genus _Lactarius_ There is little doubt that the genus _Russula_ and the genus _Lactarius_ are closely related; in fact they stand aside from the other agarics in the very important character mentioned on page 46. In Europe the easiest distinction between the two genera is that members of the genus _Lactarius_ exude a milk-like juice which may be white or variously coloured depending on the species involved (e.g. purple in _L. uvidus_ (Fries) Fries, yellow in _L. chrysorheus_ Fries). The cap, stem and frequently the gills are brittle and when broken liberate the milk-like liquid; when the fruit-body is dry, however, the presence of this liquid may be difficult to demonstrate. The spores have a blue-black ornamentation under the microscope when mounted in iodine, and although when in mass the colours are not as varied as those found in the genus _Russula_ there is every likelihood that they will play an important role in the classification of the group in the future. The colour of the spore-print has been rather neglected, although the genus includes some rather unusual fungi. [Illustration: Plate 8. Fleshy and milking fungi: Spores whitish and borne on gills] The odours of many species are very distinct and vary from the smell of coconut and spice to those of various flowers; an odour commonly met with is termed ‘oily rancid resembling butter which has become mouldy’; in early books it was described as being the smell of bed-bugs! The majority of the species are undoubtedly mycorrhizal: thus _L. torminosus_ is found with birch, _L. deliciosus_ and _L. rufus_ with conifers and _L. quietus_ with oak. Brief notes are given on additional species:-- ~L. camphoratus~ (Fries) Fries Curry-centred milk-cap _Cap_: width 20-50 mm. _Stem_: length 20-50 mm; width 4-6 mm. Cap and stem: red-brown. Gills: reddish brown. Flesh: reddish buff with an aromatic odour resembling spices which becomes very strong when dried and exudes a pale thin milk-like liquid. Common in conifer woods and plantations. ~L. deliciosus~ (Fries) S. F. Gray Saffron milk-cap _Cap_: width 50-120 mm. _Stem_: length 20-60 mm; width 15-25 mm. Cap: viscid, dirty greyish ochre with flush of tawny but soon becoming greenish with age.