Elements of Structural and Systematic Botany

-Cont

asidiom

e are other simpler and smaller ones that, according to the latest investigations, are probably related to them, though formerly regarded as constituting a distinct group. The most generally known of these lower

t the top of special cells known as basidia,[8] the number produ

heir popular name from the reddish color of the masses of spores that, when ripe, burst through the epidermis of the host plant. Like many other fungi, the rusts have several kinds of spores, which are often produced on different hosts; thus one kind of

00. D, part of the leaf of a hawthorn attacked by the cluster cup stage of the same fungus, upper side showing spermogonia, natural size. E, cluster cups (Roestelia) of the same fungus, natural size. F, tip of a leaf of the Indian turnip (Aris?ma), bearing the cluster cup (?cidium) stage of a rust, × 2. G, vertica

magnified, the masses of spores appear as bright orange spots, mostly upon the lower surface. The affected leaves are more or less checked in their growth, and the upper surface shows lighter blotches, corresponding to the areas below that bear the cluster cups. These at first appear

hat the leaf is thickened at this point owing to a diseased growth of the cells of the leaf, induced by the action of the fungus. The mass of spores (Fig. 47, G) is surrounded by a closely woven mass of filaments, forming a nearly globular cavity. Occupying the botto

olor. As the spores grow, they finally break the overlying epidermis, and then become rounded as the pressure from the sides is relie

ts and smuts. If one of these cedar apples is examined in the late autumn or winter, it will be found to have the surface dotted with little elevations covered by the epidermis, and on removing this we find masses of forming spores. These rupture the epidermis early in the spring, and appear then as little spikes of a rusty red color. If they a

ores (teleuto spores), attached to long gelatinous stalks (Fig. 47, B). They are thi

w within twenty-four hours or less. Each cell of the spore sends out a tube (Fig. 47, C), through an opening in the outer wall, and this tube rapidly elongates, the spore contents passing into it, until a short filament (basidium) is formed, which then d

w bright orange-yellow spots about a centimetre in diameter (Fig. 47, D), and considerably thicker than the other parts of the leaf. On the upper side of these spots may be seen little black specks, which microscopic exami

constitute the "black-rust" stage (Fig. 47, J). Associated with these, but formed earlier, and germinating immediately, are often to be found large single-celled spores, borne on long stalks. They are usually oval in form, rather th

and red-rust stages are pretty much the same in all. Of the commoner genera Melampsora, and Uromyces (Fig. 47, L i), have unicellular

or all of the stages. The cluster-cup stages are best examined fresh, or fro

age to wheat and sometimes to other grains. The red-rust stage may be found in early summer; the black-rust

is an example. They are jelly-like forms, horny and somewhat brittle when dry, but becoming soft when moi

inus, of which there are several species growing on the excrement of various herbivorous animals. They not infrequently appear on horse manure that has been kept covered with a glas

," or spore-bearing plates. D, section across one of the young gills, × 150. E, F, portions of gills from a nearly ripe fruit

, that diminish in number and size toward the bottom. After the cap reaches its full size, the stalk begins to grow, slowly at first, but finally with great rapidity, reaching a height of several centimetres within a few hours. At the same time that the stalk is elongating, the cap spreads out, radial clefts appearing on its upper surface, which flatten out very much as the folds of an umbrella are stretched as it o

-ball (Lycoperdon). B, earth star (Geas

f the Ascomycetes) reaches a height of two or three millimetres, and is plainly visible to the naked eye, the cap grows downward at the margins, so as to almost entirely conceal the stalk. A longitudinal section of such a stage shows the stalk to be composed of a small-celled, close tissue becoming looser in the cap, on whose inner surface the spore-bearing ridges ("gills" or Lamell?) have begun to develop. Some of these run completely to the edge of the cap, others only part way. To study their structure, make cross-sections of the cap of a nearly full-grown, but unopened, specimen, and this will give numerous sections of the young gills. We find them to be flat plates, composed within of loosely interwov

tissue, as well as in the form and size of the whole spore fruit. They are sometimes divided, according to the position of the spores, into t

forty centimetres. The earth stars (Geaster) have a double covering to the spore fruit, the outer one splitting at maturity into strips (Fig. 49, B). Ano

B, full grown. C, section through B, showing th

ut finally become exposed. Here belong the toadstools and mushrooms (Fig. 51, B), the large shelf-shaped fungi (Po

ural size. C, E, Polyporus: C, × ?; E, × ?. D, part of the under surface of D, natural

s Clavaria (Fig. 51, F), smooth-branching forms, usually of a brownis