162 



KNOWLEDGE. 



June, 1915. 



is still, as a rule, maintained, thougli it was lost 

 in the specimen photographed. In autumn the 

 bright red fructitication shown in the pliotograph 

 appears above the surface of tlie ground in which 

 the remains of the chrysalis lie buried. A larger 

 form {Cordyccps sincusis) is sold in bundles, with 

 the caterpillar still attached, as a regular article 

 of diet in China. 



Certain fungi are constantly associated with 

 the roots of several of tlie iiigher plants. This 

 association, called " Mycorrhiza," has been observed 

 especially in connection with members of the 

 order Cupuliferae (willows, poplars, beech, and 

 so on), and in a good many orchids and pines. 

 Monotropa (see Figure 1 43) is a degenerate flowering 

 plant which is entirely devoid of all chlorophyll, 

 and has therefore to obtain all its food ready- 

 made from the soil. In it the connection between 

 fungus and higher plant in the mycoirhiza is so 

 close that Mowtropa has lost practically 

 everything that can be described as an ordinary 

 root. It is probable that in mycorrhiza the union 

 between the fungus and the higher plant is in the 

 truest sense a cooperation, and that both partners 

 derive benefit from the union. Sometimes the 

 fungus threads are found inside the cells of the 

 higher plant ; sometimes only between and around. 

 They are usually most abimdant where there is 

 plenty of humus in the soil, and probably assist 

 the plant in the absorption of water, as well as 

 organic substances and mineral matter. This 

 form of partnership is probably a very old one, 

 for fossil mycorrhizae have been found in con- 

 nection with some of the plants of the Coal Measures. 

 As the fungi forming mycorrhizae but rarely form 

 fructifications, little is known of the exact nature 

 and affinities of most of them ; but the myceHum 

 of a species of Elaphomyces is said to form the 

 mycorrhiza of some conifers, and that of a Nectria 

 has been stated to act in a similar capacity in 

 connection ^\^th the roots of certain orchids. 



It is well known that bacteria are found within 

 the tissues of some flowering plants, particularly 

 of the natural order Rubiaceae, throughout their 

 whole life-history, and that they appear to be 

 quite harmless to their hosts. Similar instances 

 are recorded with regard to fungi. Within the 

 tissues of the darnel, ryegrass, and Italian rye- 

 grass (Lolium temulentmn, perenne, and italicum), 

 three common meadow grasses, the mycelium of 

 a fungus is often found. As the grass grows, so 

 does the fungus ; and when seeds are formed the 

 fungus threads enter these, and remain dormant in 

 them until they germinate in the spring. Some 

 eighty per cent, of commercial samples of darnel 

 seeds are infected with the fungus, which is there- 

 fore \\idely distributed, but not universal. There 

 are, indeed, two distinct races of these three 

 grasses, the infected and the uninfected ; but so 

 perfect has the copartnership, or symbiosis, become 



that the infected plants are actually more healthy 

 and vigorous than the uninfected. From the 

 point of view of the fungus, the cooperative existence 

 would appear to be so satisfactory that spore- 

 production of every kind has been given up, and the 

 fungus is reproduced entirely by the hibernating 

 mycelium, which is carried from generation to 

 generation in the seed. As there arc no reproductive 

 bodies, the nature of the fungus cannot be deter- 

 mined. 



Fungi differ greatly in consistence. Some are 

 as hard and dry as boxwood (see Figures 142 and 

 144) ; others are as soft as jelly, and contain 

 ninety per cent, or more of water (see Figures 145 

 and 146). Fungi contain large quantities of a 

 variety of cellulose, called " fungus cellulose " ; 

 glycogen is also very often found in them, and 

 glucose, mannite, and other sugars are frequently 

 present. The cap and stem of Boletus edidis (see 

 Figure 149) contain sugar, but this substance is 

 absent from the tubes, and perhaps it is for this 

 reason that, while the flesh of this toadstool is 

 often found eaten by slugs, the spore-bearing tubes 

 are hardly ever touched. Fats and fatty acids are 

 present in varying proportions in different species, 

 and amount to six per cent, in Lactarius deliciosus. 

 The percentage of mineral salts is also high, and 

 reaches six to twelve per cent, of the dry solids. 

 The salts are mainly those of potassium, with smaller 

 quantities of iron and manganese. Fungi also 

 contain a relatively high proportion of nitrogen, 

 and from two to five per cent, of the dry solids 

 consist of this element. Only about one-half of 

 the nitrogen is, however, combined as proteid, 

 and only one-seventh of it is digestible proteid. 

 It will thus be seen that the edible fungi are not in 

 reality as nourishing as was at one time supposed. 

 The percentages of digestible proteids, carbohy- 

 drates, and fats present in the mushroom — the 

 most nourishing of the fungus tribe — are almost 

 identical with those of cabbage — a vegetable that 

 can usually be much more safely eaten. Several 

 fungi also contain poisons, or substances which 

 rapidly change to poisons in the earliest stages of 

 decomposition. Though very deadly, the poisons 

 are often present in minute quantities only, and 

 it is said to require about two hundred pounds of 

 the poisonous Fly Agaric [Amanita fiiuscaria) (see 

 Figure 1 1 9 on page 1 36) to produce one ounce of 

 muscarine — its poisonous principle. Oxalate of lime 

 is present in the walls of the hyphae of many fungi, 

 and is said to be of value as a protection against 

 slugs ; it is especially abundant in the mycelium of 

 the Stinkhorn (Phallus impudicus) (see Figure 148). 

 Tannin has probably a similar function. It exists 

 especially in the outer hyphae of sclerotia and 

 rhizomorphs. The growing hyphae of many 

 parasitic forms also contain enzymes and ferments 

 capable of dissolving starch and removing the 

 lignin from woody cells. 



One of the most striking things about a good 



