Yellow patches are formed on the large leaves of _Arisarum_ by a species of parasitic Alga, _Phyllosiphon_, which lives in the mesophyll. Many tropical leaves are spotted yellow by epiphytic Algae--_e.g._ _Cephaleuros_. It must be noticed that many fungi produce yellow spots or flecks in the earlier stages, which turn brown or black as the fructifications appear, _e.g._ _Dilophia graminis_, _Rhytisma acerinum_. The yellow-spotted leaves of _Farfugium grande_ (_Senecio Kaempferi_) are so like those of _Petasites_ attacked with _Aecidium_ in its early stages, that an expert might be deceived until the microscopic analysis was completed. _Red spots_, varying from rusty or foxy red to bright crimson, are the symptomatic accompaniment of several fungi, the former often characterising the teleutospore or aecidium stage of Uredineae--_e.g._ _Aecidium Grossulariae_--the latter sometimes indicating the presence of Chytridiaceae. Red spots are also caused by _Gloeosporium Fragariae_ on Strawberry leaves, _Polystigma rubrum_ on Plums. Crimson spots on Apple and Pear leaves are also due to _Phytoptus_: they turn brown later. _Brown spots_ or flecks, varying in hue from dull slaty brown to deep red browns, are a common symptom of Fungus and Insect diseases, the colour often indicating the death of the tissues, rather than any special peculiarity of the action of the parasite. Good examples are furnished by the Potato-disease, and by _Peronospora viticola_, _Sphaerella vitis_ and other disease-fungi of the Grape Vine. The teleutospore stage of many Uredineae also occurs in deep brown spots. Black spots and flecks are exceedingly common symptoms of the presence of fungi, _e.g._ _Fusicladium_ on Apples and Pears, and the pycnidial and ascus stages of many Ascomycetes--_e.g._ _Phyllachora graminis_. The teleutospore stages of species of _Puccinia_, _Phragmidium_, etc., are also so deep in colour as to appear almost black. _Scab_ on Pears is due to the presence of _Fusicladium_, which indurates the outer skin of the fruit causing it to crack under pressure from within, and to dry up, the deep brown to black patches of fungus persisting on the dead surface. Black spots on grasses and sedges are caused by Ustilagineae, and are commonest in the grain, the soot-like powdery spores (Smut) being very characteristic. _Ustilago longissima_ induces black streaks on the leaves. Many of these fungi cause distortions or pustules on leaves and other organs. Brown and black leaf spots are frequently furnished with concentric contours arranged round a paler or other coloured central point--_e.g._ _Cercospora_ on Beans, _Ascochyta_ on Peas. Brown spots with bright red margins are formed in young Beans by _Gloeosporium_. Species of _Fumago_, _Herpotrichia_, etc., may cover the entire surface of the leaf with sooty patches, or even weave the leaves together as if with black spider-webs.