STUDIES IN LAKE AND STREAMSIDE VEGETATION 159 



Secondary species of the floor are for the most part such as grow also 

 in the shrub zone around the lake. Examples of these are Lonicera 

 involucrata, Ribes parvulum, Pyrola secunda, Moneses unijlora, Pedicu- 

 laris racemosa. 



V. Seasonal Aspects 



General Account. — As shown in the account of climatology, the 

 growing season is short. In 1908 freezing temperatures were recorded 

 every week of June and as late as July 7. The first autumn frost came 

 September 1. It is evident that spring-blooming plants must be few. 

 They can be only alpine species or such forms as enter into the formation 

 of the pre-vernal flora at lower altitudes. 



The Seasonal Limits. — As a convenient classification spring may be 

 said to begin about May 15 and extend to July 1; summer, July 1 to 

 August 15 ; autumn, August 15 to October 1. Naturally such a division 

 into seasons will seem somewhat unusual when, in most climates of the 

 north temperate world, three months, June, July and August, are reck- 

 oned as forming the summer. The very short period of warm weather, 

 however, makes the seasons only about six weeks in length. The 

 special characters of each season 1 will be more fully set forth in the 

 following paragraphs. 



Spring Aspect. — Early in the season the soil of the sedge zone is cold. 

 Because of its excessive moisture even the soil surface does not easily 

 become warm. So there is little fresh vegetation in the early part of the 

 season. In fact the sedge zone is brown with the dead plants of last year 

 until late in June. Among the plants of the shrub zone the flowers of 

 the willows and birches come out about June and the leaves are full 

 grown a few weeks later. In the forest zone the soil is quickly warmed 

 at the surface by the direct heat of the sun permitting the early growth 

 and blooming of a certain number of species. These occur, for the 

 most part, in open places where there is free access of sunlight. As 



1 A useful account of seasonal aspects in the mountain regions near Pike's Peak is given by Professor 

 Frederic E. Clements in his "Formation and Succession Herbaria" {Univ. of Neb. Studies, Vol. IV, pp. 

 320-55, October, 1904) where he lists the species of each aspect. On page 346 is a list of the species in the 

 "meadow thicket formation" of the sub-alpine zone, corresponding to our "shrub zone" at Redrock Lake. 

 The aspects are much the same in these two parts of Colorado. In alpine districts he recognized only two 

 periods, early and late; spring, summer and autumn not being distinguished. 



