30 STOCK-POISONING PLANTS OF MONTANA. 



other hand, the large size or coarseness of the plant does not appa- 

 rentl}' exercise an}" influence in preventing- cattle from eating it. It 

 is a most noticeable fact in connection with a class of poisonous plants, 

 such as Zygaden ^t^ (death camas) and the smaller species of larkspur, 

 that the seeds ripen and the whole plant dries up very cjuickl}' after 

 flowering. The death camas seems to be especially tempting to sheep 

 just before the flowering stem is formed. Very soon after the flowers 

 have opened, however, the leaves and stem turn yellow and the plant 

 shrivels and becomes much less conspicuous than when in a green 

 condition. Similar statements may be made concerning the smaller 

 species of larkspur. 



Thus far the vegetative stage of poisonous plants has been considered 

 only with reference to its influence upon the selection of the plants by 

 stock for forage. It is hardly necessary to observe that poisonous 

 plants can do no harm to stock except as they are eaten. One of the 

 most practical problems, therefore, in connection with the study of 

 poisonous plants is the determination of the circumstances under which 

 stock eat them. 



VARIATION AND LOCALIZATION OF THE POISONOUS SUBSTANCES 



IN PLANTS. 



There is another group of facts, partly dependent on stage of 

 growth, partly not. which have an important influence on the danger- 

 ous character of poisonous plants. It is found to be true, as will now 

 be shown, that certain parts of a plant may be poisonous while others 

 are comparativelv inert, and that the quantity of poison may vary in 

 the same parts of the same species under diflerent conditions and 

 especially at diflerent stages of growth. It is also true that the poison- 

 ous principle of a plant is often located in a particular part of a seed 

 or a leaf, so that it is possible that a portion of that organ ma}- be 

 eaten with impunity while other parts would prove fatal if eaten. It 

 will readil}' be seen that the reputation of a plant as poisonous or non- 

 poisonous may be aflected by these circumstances; since, for example, 

 if a plant is poisonous only at a stage when it is not eaten, its poison- 

 ous character would not have opportunity to show itself. 



Few of the plants discussed in this report are of sufficient commercial 

 importance to have been studied chemically with anything like the 

 detail necessary in order to draw definite conclusions in regard to the 

 development of their characteristic poisons and their location in the 

 various organs. But it is certain, in the case of the larkspur, at least,- 

 as will be shown in the later discussion, that there is marked variation 

 in the quantity of the poisonous substances in the leaf before and after 

 flowering. This may be the case with the leaves of the death camas, 

 but as this plant is not attractive to stock after flowering the question 

 is of less practical importance. It is of interest to note, however, that 



