222 BULLETIN UNIVERSITY OF MONTANA 



very striking. (Fig. 7.) In the older trees it is split up into long rhom- 

 boidal plates, covered with scroll-like yellow scales, very much resembling 

 those of the western larch. At this stage the tree is known by certain 

 lumbermen as the yellow pine. In the younger trees the bark is more 

 ridged and rounded, and does not have the yellow color. This form goes 

 under the name of bull pine. In the older trees the bark is two to four 

 inches thick and very resistant to fires. 



In the Flathead valley the tree is confined to the low altitudes, and 

 is more abundant on the border of the prairie, though it does better in 

 moister situations. It is, perhaps, shaded out of these places because of 

 its extreme intolerance of shade. It needs very open places in which to 

 germinate, and very little shade will prevent this. The bull pine and its 

 closely related form, the rock pine (Pinus ponderosa scopulorum 

 Engelm.), are found throughout the western part of America. The latter 

 has not been reported from Montana. 



The lodgepole pine (Pinus Murrayana "Oreg. Com.") : The leaves of 

 the lodgepole pine are in pairs one to two inches long, and remain on the 

 trees seven to eight years. The cones are smaller than those of any 

 other pine in Montana. The tree resembles the jack pine (Pinus divari- 

 cata (Ait.) Du Mont de Cours.) of the eastern part of the United States 

 in its general appearance and some of its habits. The bark of smaller 

 trees is smooth. On the older trees it breaks up into rectangular plates, 

 and is about one inch in thickness. It is a tree easily destroyed by fire, 

 but because it can produce cones at a very early age, it has a very great 

 advantage over the other trees in gaining a foothold in burned areas. 

 Groves of small trees six to ten years old may produce cones abundantly. 

 Another remarkable feature of the lodgepole pine, is that the scales of 

 the cones remain closed, sometimes for several years, thus preserving 

 the vitality of the seeds for a comparatively long period. The seeds from 

 cones nine years old have germinated. The heat of the fires sweeping 

 through a forest will open cones, liberating, though not often destroying 

 the seeds, which germinate at once, and thus give a decided lodgepole 

 pine aspect to the new growth. In closed forests the lodgepole pine has 

 small diameter and great length. Trees over a hundred feet tall often 

 are no more than six inches in diameter. Where there is plenty of room 

 for the lodgepole pine to grow the dameter is greater, and the height 

 less. The lodgepole pine has a rather wide distribution in western 

 Montana. It is usually confined to rather moist situations. So success- 

 ful has it been in gaining a foothold after fires, that it has replaced many 

 square miles of valuable timber. It cannot tolerate shade, however, 

 and' if fires are kept out, in several generations the forest conditions will 

 probably be the same as before the original forest was destroyed. 



The giant arbor-vitae and the Rocky mountain juniper are easily dis- 

 tinguished from the remaining conifers by their scalelike leaves. In the 

 giant arborvitae they closely overlap. In the Rocky mountain juniper 

 they do not overlap so closely. 



The giant arbor-vitae (Thuya plicata Don.) (Thuya gigantea Nut- 

 tall) : This tree resembles its eastern relative the arbor-vitae (Thuya 

 occidentalis Linn.) very closely, both in appearance and in habits. (Fig. 



