infest the same area. The Canada thistle is a native of Europe and Asia. In Great Britain it is called corn or creeping thistle. Its growth is rather slender, and from one to two feet in height. Its deep-laid, extensively-creeping and sprouting rootstock make it one of the very worst of weeds. Both of these plants are constantly invading new territory, especially such as is continually cropped in wheat. The areas infested become useless for growing small grain. Intensive cultivation with a certain amount of hand work is the best remedy.

General Remedies.-While experiments in killing certain weeds by spraying with chemical solutions have been made, the most practical method is to prevent as far as possible the spread of their seeds. This is accomplished by sowing clean seed wheat, and by killing the weeds when they do succeed in starting. Conditions most favorable to the growth of wheat place the weeds at the greatest disadvantage. Intensive farming always finds effectual methods of dealing with them.

Losses. The wheat growers lose millions of dollars annually on account of weeds. They are the largest factor in elevator dockage. In North Dakota' 47 samples of wheat were found to have an average real dockage of .64 pounds per bushel. This varies each year, and the average dockage for the 1906 crop of wheat was about 2 pounds in the Minneapolis market. If 500,000,000 bushels of wheat are grown in the United States annually, and the dockage averages only half of one pound per bushel, then over 4,000,000 bushels are not only waste, but they also injure the commercial value of the real wheat. Where large quantities of wheat are cleaned, the cost is about onefourth of a cent per bushel.

Birds. In the United States 29 species and subspecies represent the family Icterida, a group of birds including those commonly known as bobolinks, meadowlarks, orioles, blackbirds, grackles and cowbirds. Rating the blackbirds in the order of their grain-eating propensities revealed by stomach examinations, and putting first those that eat least, the list reads: Bobolink, redwing, cowbird, rusty blackbird, yellowhead, crow blackbird, boat-tailed grackle, Brewer's blackbird and California redwing. Since the first two are the ones most complained of, the amount of grain actually eaten would not seem to be the 1 N. D. An. Report (1904), p. 45.

only factor to be considered in determining the relative harmfulness of the species. The dove, the sparrow and the crow also eat grain from the fields, as do many other species. None of these birds are, however, entirely harmful; indeed the good that many of them do by destroying injurious insects and seeds more than counterbalances the damage occasioned by the eating of grain. At least 50 different birds act as weed destroyers and help to eradicate nearly 100 species of noxious plants. The number of weed seeds eaten is enormous, one bird eating a thousand seeds of some kinds for a single breakfast. The insects eaten by these birds are also generally noxious. There is usually an equilibrium of organisms in nature, and birds become harmful only when they disturb this proper balance by increasing out of proportion to their environment.

"Yellow Berry."-This occurs in hard winter wheat. Some of the wheat berries are often lighter in color and weight than the hard red ones, and also have a lower gluten content. Overripeness and failure to stack the sheaves have been given as causes, but opinions seem to differ as to this. It is claimed that the annual loss in Nebraska is from one-half to one million dollars.'

FUNGOUS ENEMIES

"Glume Spot."-This fungus receives its name from the dark spots that it causes upon the glumes of wheat. It has been studied but little, and no remedy is known.

Wheat Scab (Fusarium culmorum) also attacks the glumes and causes lead-brown-colored sections in the spike, or even destroys the spike entirely. The loss is usually light, but may reach a maximum of about 15 per cent. The only remedy sug gested is the burning of the stubble.

Smut. Two kinds of smut attack wheat, stinking smut, or bunt (Tilletia tritici (Bjerk.) Wint.), and loose smut (Ustilago tritici (Pers.) Jens.). The enormous damage resulting from this disease attracted attention in ancient Greece and Rome. Hartlib called attention to the fact that smutty seed produces smutty grain, and he was perhaps first to record a remedy (1655). His three remedies for smut in wheat were liming the 1 Neb. Bul. 89 (1905), p. 50.

THREE THRESHING OUTFITS IN OPERATION ON AN OKLAHOMA RANCH

field, liming the seed, and soaking the seed over night in common salt lye. Though the efficacy of the remedies was doubted, there must have been some beneficial results, for it is claimed that the seed was invariably steeped. By the middle of the nineteenth century there were many methods of steeping, liming and brining wheat to prevent smut. It was found that the use of a solution of arsenic gave a clean crop from smutty seed.

on

Just how fully the nature of smut was understood by these early writers does not seem to be clear, but they must have had considerable knowledge of the disease in order to pursue such correct principles in endeavoring to effect a cure. The black dust frequently filling the kernels of ripening wheat consists of thousands of germs of the parasitic smut fungus. These germs, or spores, have a great capacity for spreading over the fields, but the only real danger seems to be from those spores which lodge on healthy kernels, generally in the hairy ends. Chances are slight of clean seed being infected by being sown ground containing smut spores. Spores have the same function as seeds of higher plants, and, the infected kernels of wheat being sown, the spores germinate at the same time as the wheat. The slender filaments penetrate the tissues of the wheat plant before the first leaf is put forth. From this point its growth is within the wheat plant, both plants growing together. It seems to be still undecided how these threads proceed below the upper two joints of the mature wheat plant, whether they pass upward through the pithy region of the stalks, or whether they follow the surface tissues, but it is probable that the method of smut growth is uniform throughout the entire plant. The fungus seems to die as it passes upward, and leaves few traces of its path.

In the mature wheat plant smut seems to be found only in the chlorophyl bearing parenchymatic tissues. Nearly 30 rows of breathing pores in the skin covering of the straw run lengthwise with the stalk. Under these rows of pores are layers of succulent cells which produce the food eventually used in forming the wheat grains. The smut filaments remain close to the open pores, absorbing and taking the place of this cellular structure with its chlorophyl and protoplasm. No other cellular tissues are disturbed, and until the heads develop the

presence of the smut can scarcely be detected without the aid of a microscope. A mass of smut threads then absorbs all the nourishment, fills the flower or grain, and soon converts it into a mass of spores. As the parasite lives at the expense of its host, the latter is weakened and stunted in proportion to the amount of smut. This may be great enough to dwarf the plants so as to prevent the formation of heads, or even to cause the stalks to die back to the ground, or it may be so little that the heads are never reached, simply the straw being infected. Much of the straw may be thus infected, greatly reducing the yield, even though apparently uninjured heads are formed. Smut filaments have also been found in grains which had formed starch. In general, smut and wheat seem to de

d

SECTIONS OF SMUTTED WHEAT STRAW

At the left is a longitudinal section of a wheat straw and at the right a cross section. a, epidermal cells; b, smut filaments; c, fibrous cells; d, internal tissues.

mand about the same meteorological conditions for their best growth. Smut will successfully pass the winter, even upon the open ground in North Dakota. Germs two years old have not lost their power of producing smut in a crop.

Grains of wheat affected by stinking smut are slightly larger and more irregular than healthy ones. Such kernels, the socalled "smut-balls," are easily broken open, and the darkbrown powder with which they are filled has a very disagreeable and penetrating odor that pervades the whole bin of wheat, even if only a small per cent of the kernels are smutted. On this account they differ from all other grain smuts in that their presence can be easily recognized. Sometimes 1 Bolley, Proc. Tri-State Grain Growers' Ass'n., 1900. p. 86. 2 Rept N. D. Agr. Exp Sta., 1901, p. 34.