MISTLETOE OF JUNIPERS 
The mistletoe of junipers is common in western and southwestern 
United States. A great deal of damage is annually caused by this and 
other mistletoe diseases of trees. 
SYMPTOMS 
In the juniper material provided, NoTE :— 
1. The irregular and gnarled hypertrophies. 
2. The mistletoe plants firmly rooted in the host-tissue. 
3. That in many cases, the growth of the branches beyond 
the parasite is stopped. 
Make prawincs showing the above symptoms. 
ETIOLOGY 
The parasite causing this disease of junipers is Phoradendron juniperi- 
num Englemann, one of the many species of the family Loranthaceae, a 
group of the flowering plants. This mistletoe has only very aborted 
leaves. They are mere scales closely appressed to the stem. 
Life-history. The inoculum in the case of the mistletoe is the small 
pulpy berry with its single inclosed seed. The berries are mature in 
Texas about December. Birds seek the berries for food and serve to a 
large degree as the disseminating agents. The stickiness of the pulp of 
the berry causes it to adhere closely to the branch of the host. 
In the material provided, OBSERVE :— 
4. The character of the berry, its pulpy flesh and the enclosed 
seed. pDRaw. (See also bulletin mentioned below, fig. 1.) 
copy Pl. Ind. Bur. Bul. 166, fig. 2 and 3, showing the method of germina- 
tion of the mistletoe seed and the penetration of the host-tissue. 
The seedling establishes its root-like sinker in the conducting tissue of 
the host and obtains, not only water, but a certain amount of raw and 
modified plant-food from the host. The mature parasite blooms in 
December. The seeds require one year to develop and mature, so that 
they are ready for dissemination the next December. 
Pathological Histology. In the small branches of juniper cut longi- 
tudinally and transversely, study the roots of the mistletoe. OBSERVE :— 
5. The size, shape and number of roots sent from a single plant 
into the host-tissue. What tissues are invaded? pRaw. 
In the prepared cross-sections of juniper twigs, OBSERVE -— 
6. The penetration of the host-tissues by the mistletoe root. 
7. The elements present in the normal wood and bark. 
8. The elements present in the root of the mistletoe. 
9. The ultimate connection between the conductive elements 
of the host and of the parasite. 
Make DRAWINGS; (a) to show diagrammatically the relation of the 
tissues of the host and parasite, outlining the tissues; (b) to show in detail 
the ultimate connection of the conductive elements. 
REPORT 
; 1. Outline a practical method for the control of. the mistletoes 
in forest areas. Explain why it should be effective. Indicate the weak 
points in the program. 
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