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A. G. Tansley. 
slope descending into Bear Canyon—the site of the next camp—there 
is a closer but still sparse wood of yellow pine with Arbutus arizonica 
Ceanothus Feudleri, Arctostaphylos Pringlei, jfuglans major, Quercus 
Gambelii, Rhus elegantula, Berber is Wilcoxiana, etc. 
On the morning of September 24th most of the party returned 
to Oak Camp en route to Tucson and the Grand Canyon of the 
Colorado River, hut a party from the Desert Laboratory accompanied 
by a few members of the international party continued the trip to 
Mount Lemmon on the summit of the Santa Catalina range. The 
south-facing side of Bear Canyon up which the route lay is a 
nearly vertical slope so dry and fully exposed to the sun that many 
desert plants go right up to the summit between the evergreen oaks 
and manzanita scrub. There are no pines on this face. Immediately 
the summit is reached, at a height of about 7,000 feet, one enters a 
fine open forest of Pinus arizonica with species of Arctostaphylos, 
Quercus emoryi and Ceanothus Feudleri as undergrowth. The trail 
winds through this forest round the valley sides for a considerable 
way, and magnificent distant views of the lower slopes and the 
desert are obtained. In the damper shaded valleys deciduous trees 
and shrubs like Acer interior (of the Negundo type) and Alnus 
acuminata occur. At about 7,800 feet the manzanitas, Arbutus and 
Quercus emoryi disappear and isolated trees of Pinus strobiformis 
are met with. In the pine-wood at this level a whole set of 
herbaceous “ montane ” plants are found: the beautiful Aquilegia 
chrysantha and Lobelia Grewiaua by damp stream-sides, Potentilla 
Thurberi , Heuchera rubescens, Oreoliriou ( Sisyrinchium ) arizonicum, 
Gilia Thurberi , with Pteridium aquilinum and Achillea Millefolium. 
In a north-facing canyon a thick stand of Douglas spruce with 
Abies concolor and fine trees of Acer grandidentatum with deciduous 
undergrowth indicate a still higher zone. Beyond, a flat-topped 
ridge, more than 8,000 feet above the sea, is traversed, with fine forest 
of yellow pine; and a short but steep descent brings the trail to 
Marshall Gulch, the last camping ground. The nights in Marshall 
Gulch at this time of year are very cold, a thick layer of ice being 
formed on the water left overnight in pails. Marshall Gulch is 
occupied by Douglas spruce wood ; associated with the dominant 
are Abies coneolor and Pinus strobiformis, with Acer grandidentatum, 
Populus tremuloides, Alnus acuminata, Quercus submollis. A rich 
“ montane ” ground-flora occurs in the wood, a majority of the 
forms belonging to genera also occurring in northern Europe, such 
as Rubus, Ribes, Cortius, Silene, Aquilegia, Aconitum, Actcea, Viola, 
Fragaria, Agrimonia, Lathy rus, Vicia, Trifolium, Heracleum, 
