The plant life of the immediate Tamalpais region is abundant and interesting; the flowering plants are represented by about eighty orders, three hundred and fifty genera, and from seven to eight hundred species, of which about one hundred are trees and shrubs.[F] Some of the Sierra forms occur on Mount Tamalpais, and it is also the locus of the most southerly extension of certain boreal species. Owing to the wide range of temperature, moisture conditions, and exposures, many of these plants can be found in bloom during every week in the year. During the warm, moist autumn and winter the hardiest species bloom from October to April in protected areas, and in the cold, exposed areas these same species require the heat of the season from April to September to bring them into bloom. Thus, within a radius of four or five miles from the summit there is not a week in the year when the flowers of certain species can not be gathered--this in face of the fact that during the months of December, January, and February the summit may be covered with sleet or snow for a day or two at a time. [F] Estimated by Miss Eastwood, curator of the Department of Botany of the California Academy of Sciences. Mount Tamalpais is therefore a point of great interest to the sight-seer, the tourist, and the student of Nature. [Illustration: View of Summit from a Point Sixteen Hundred Feet above Tide.] MODES OF REACHING THE SUMMIT.--For many years a trail has existed from Mill Valley to the summit, and another from Ross Valley, both practicable for pack mules. Later the Ross Valley trail was improved so as to be practicable for light vehicles, but these did not answer the needs of the increasing travel, and in 1895 the Mill Valley and Mount Tamalpais Scenic Railway Company was organized. The purpose of this company was bold--to construct a traction railroad from tide level to the summit of a peak not two miles off and nearly half a mile high appeared visionary, if not impossible, to many. But with persevering skill a road was located upon a line 8.19 miles long, having an average grade of five and a half per cent and maximum grades of seven per cent, and overcoming 2,353 feet elevation in this distance. Four and nine tenths miles are curved, the minimum radius being seventy feet. Owing to the rough and ravine-cut topography, twenty-five trestles were necessary, the curvature and grade being maintained over these. In order to reduce the cost of grading and to develop sufficient length to overcome the elevation, the grade contour was followed as closely as possible. The very short radius employed permitted this to be done without tunnels and with but two through cuts. The accompanying map, prepared from the United States Coast and Geodetic charts and the maps and profiles of the company, gives a general idea of the location and main features. To the student of railroad location it forms an interesting exhibit of the extreme flexibility of railway location.