4 
Colorado Experiment Station 
food that appears in the spring time. Again in the late summer 
the native grasses often cure early from drought and injurious 
plants like loco and lupine remain green. It is obviously true that 
stock will eat most poisonous plants that are green in preference 
to grass that has dried up and this no doubt accounts for the loco 
habit being acquired more often in the late summer and fall. 
The stage of growth has much to do in determining whether 
or not certain plants will be eaten at any particular season of the 
year. The larger species of larkspur and the water hemlock be¬ 
come coarse and objectionable after flowering and are seldom eaten. 
On the other hand some plants are relished throughout the period 
of their growth. The death camas is eaten with avidity just before 
the flowering stem is formed; equisetum is eaten more after being 
cured with the hay; and matured lupine with the seed pods appears 
to be relished by sheep. To analyze all of the conditions under 
which poisoning occurs seems to be a« hopeless task. The subject 
is complex. In the realm of poisons we are still groping in the dark, 
and there are many mysterious cases of poisoning that are quite 
unaccountable. 
The reputation of a plant as poisonous or non-poisonous may 
be affected by many circumstances. It is found to be true that cer¬ 
tain parts of a plant may be poisonous while other parts are not, 
and that the quantity of poison in any particular part mav vary 
widely under different soil and climatic conditions and at different 
periods of growth. It is necessary to know the entire history of a 
plant before declaring it poisonous or non-poisonous. For example, 
the poison in lupines is confined almost. entirelv to the se'-ds, and 
if cut before going to seed makes a fair quality of hay. In water 
hemlock the poison is found largely in the roots of the mature plant. 
In calabar bean the very poisonous alkaloid eserine is found In the 
cotyledons. In aconite seeds, the central part contains most of th^ 
aconite. Not only may the amount of poison in any particular part 
of a plant vary greatlv at different stages of growth but it has been 
shown by Dr. J. P. I^odsy in Java that in case of cinchona the 
amount of alkaloid in the leaves varies greatly between night and 
day and that the alkaloid is formed in the leaves during the dnv 
and deposited in the branches or bark during the night. Because of 
the fact that the most active principle in most plants is not uniform¬ 
ly present in any particular part of the plant, there is, as might be 
expected, contradiction in rating olants as poisonous or non-poison¬ 
ous. It is a matter of common observation that while a large num¬ 
ber of animals in a herd may be poisoned, a few almost invariablv 
escape, and all are seemingly under the same conditions. The num¬ 
ber poisoned and the degree of poisoning depend upon three factors: 
The quality of poison, the quantity of poison, and the racial as well 
as individual susceptibility to the narticular poison in nuestion. 
There is the e'reatest diversitv in animals as to susceotibilitv to pois¬ 
ons-. In Prof. Pudolnh Keb^rt’s text on Practical Toxicolop'v is 
found the following information bearing on this subject: ‘‘The 
