EVERGREENS OF COLORADO 



67 



animation of one of these matted growths of twigs will usually reveal 

 the presence of numerous greenish yellow stems growing from the sur- 

 face of the twigs or of the branch to which they are attached. These 

 little stems belong to one of the small species of mistletoe which infest 

 the different members of the pine family. These are small, leafless plants 

 which produce minute flowers and later give rise to small whitish berries 

 containing seeds covered with a sticky substance. When the berries are 

 mature toward autumn they burst and expel the seeds to a distance of 

 several yards. On account of the sticky covering, the seeds may lodge 

 upon the twigs and branches of nearby trees and start the growth of the 

 plant in a new location during the following spring. In some cases a 



badly diseased branch may die 

 and fall away, leaving a canker- 

 like wound in the side of the tree 

 trunk. Badly infested trees, 

 however, may be entirely killed 

 by this parasite. While the mis- 

 tletoe disease of our ever- 

 greens is seldom so severe as to 

 warrant any radical measures in 

 its extermination, wherever it at- 

 tacks trees which are especially 

 desired for their proximity to 

 summer resorts or mountain 

 homes it may be necessary to 

 combat this trouble by cutting 

 off and burning all of the dis- 

 eased growths as soon as they 

 appear. 



Our native cedars are subject 

 to certain rust fungi which pro- 

 duce little galls known as cedar 

 apples upon the newer growths. 

 These appear in spring during 

 moist weather in the form of 

 slight enlargements or swellings 

 covered with gelatinous out- 

 growths from which the spores 



Fig. 53. Engelmann Spruce, near tim- 

 ber-line, showing effects of wind. 



of the disease are given off. These spores which are microscopic in size 

 readily float in the air. When these spores come in contact with the 

 new foliage of certain plants of the apple family such as the service 

 berry, hawthorn, quince and pear, they are capable of setting up a dis- 

 ease known as the cluster cup fungus. This may be recognized by the 

 formation of swellings of a yellowish or orange color which are produced 

 on the leaves and sometimes upon the fruit of the affected host plant. 

 These swollen, discolored portions contain numerous minute spore pro- 

 ducing cavities from which spores are given off, capable of re-infecting 

 the cedars which may be near at hand. For this reason, it is unwise to 



