Translation of De Vries' Mutation Theory, 109 



few days of bright sunshine to bring them to the blooming stage. 

 These plants complete their growth after blooming and examin- 

 ation in the autumn reveals the rudiments of the next years' 

 blossom tightly curled up in the heart of the plant. Digging 

 them from under the snow as early as April one finds them green 

 and already lengthening the flower stock. I do not suppose they 

 are ever totally imresponsive to sunshine and a warmer day than 

 usua', even in winter, causes them to unfold a little and, as their 

 roots do not jenetrate far below the surface, water from the 

 melting snow furnishes additional stimulus. Probably they 

 merely curl up and suspend animation during the colder days and 

 are ready to burst into bloom as soon as the first bare slopes ap- 

 pear. Indeed, I have often found Thlaspi coloradense pushing 

 fully expanded blossoms through the snow at the edges of the 

 drifts. Summer, from about the first of July to the middle of 

 August, marks the height of the growing season and all the 

 characteristic alpine species are in full bloom. Autumn is char- 

 acterized by the ripening of the grasses and the blooming of those 

 species which have crept up from below t'mber line. These 

 plants withstand a noticeable degree of frost and are mostly 

 such as the gentians, whose reproductive organs are well pro- 

 tected; but even as late as November a few warm days after 

 quite severe weather will bring out quite unexpected blossoms 

 of Potentilla saximontana and Cerastium occidentale. 



The autumn landscape above timberline is by no means 

 cheerless. The deep blue sky is overhead; the yellow grass be- 

 neath, sloping down to the green of the pines and the red and 

 orange and gold of the aspens, is broken by dense splashes of 

 blue harebells and creamy gentians, while away on the horizon 

 tower the glistening white peaks swimming in the purple haze 

 of Indian summer. 



THE TRANSLATION OF DE VRIES' MUTATION THEORY. 



By D. T. MacDougal 



The first American review of the mutation theory was printed 

 in Torreya in 1902 (MacDougal, D. T., Torreya. May, June, and 



