DISEASES OF SHEEP 623 



more or less infected with a fungus (Puccinia xylorrhizae) . If it 

 should prove to be true that the malady is due to the eating of the 

 Aster then it may be the Aster itself that is the source of the trouble, 

 but the chances are rather better that the specific poisonous qualities 

 are due to the fungus. 



Description of the Plant. To those who are familiar with the 

 range it will be possible to describe the plant so that it can be recog- 

 nized. It need only be looked for upon gumbo clays, usually on 

 gentle slopes or sometimes on ridges. Often these conditions are met 

 with in the neighborhood of temporary ponds or lakes where the 

 sheep are watered. The plant has a strong woody root, more or less 

 branched just at the surface of the ground. From these woody 

 crowns, tufts of short branches spring. These bear green, narrow 

 leaves, one or two inches long, the whole tuft becoming at length sev- 

 eral inches high and finally producing in June, a considerable nurn- 

 ber of large white daisy-like flowers with a yellow center. If the 

 leaves be examined it will be found that they usually bear a consid- 

 erable number of yellowish or brownish spots, caused by the fungus 

 previously mentioned. 



The time when the foliage first appears will vary -with each year. 

 Again, the time of blossoming is a matter of weather conditions. So 

 far as it is known, sheep are the only species susceptible to poisoning 

 by the Woody Aster, and of these the greatest losses are reported in 

 old pregnant ewes in early spring and in lambs late in summer. 



In the spring we experience more wet weather and the plants are 

 resultingly more active as well as more inviting in appearance. Over- 

 crowding of the range at this time urges the consumption particularly 

 of the greener, more advanced vegetation over the less matured 

 grasses. 



The greatest losses naturally occur after shearing, when the 

 fasted sheep are of necessity driven across patches of the Aster plant. 

 The sheep, having little time to choose their food and urged by hun- 

 ger, grasp the plants most attainable, i. e,, the Aster, since its ranker 

 growth allows it to outstrip and stand above the natural grasses. It is 

 at this time, also, the flowering period of the plant or just previous to 

 it, that the leaves of poisonous plants are considered to be the most 

 active. There can be no doubt but that wet weather favors poisoning 

 by the Aster, just as its toxicity is affected by various stages of its 

 growth, but at present we can only theorize as to the reason. 



Puccinia. That fungi of various kinds are known to be poison- 

 ous furnished one reason for suspicion towards the Woody Aster, 

 which has been almost invariably infected and markedly so, by the 

 Puccinia xylorrhizae. The occurrence of the fungus on the Aster is 

 a factor of importance in this problem. Even though it might not 

 possess poisonous activity of its own, it is conceivable that the Aster 

 may be sufficiently nitrogenous so that the numerous fungi may oc- 

 casion a chemical change in the material similar to ptomain produc- 

 tion by bacteria in the decomposition of foods of animal origin. As 

 the Aster gives off a pronounced and extremely disagreeable odor as 



