200 Atkinson. 



are red is nutans, green in pycnocarpa, although in age a tinge of 

 red particularly on the sunny side of the stem, often appears in pyeno- 

 carpa, but does not appear over the entire surface. The stems are 

 normally red in nutans due to the quantity of anthocyanin characteristic 

 of a number of Oenothera species. The red coloration of the stems and 

 mid veins of nutans is also a prominent and constant character under 

 normal conditions. When the plants are shaded during growth the stem 

 coloration may appear late and be of less intensity and extent than 

 under normal conditions. The amount is small in pycnocarpa. The red 

 color is always present in the roots of the two species, occupying a 

 concentric zone midway between the medulla and the periderm, but the 

 pigment is more abundant in the roots of nutans than in those of 

 pycnocarpa. It its also present in the roots of their hybrids. The 

 tubercles of the stem, normally green in pycnocarpa, are often red 

 over the reddish areas of the stem, but the color is not so deep as 

 in nutans. 



The red spotting of the leaves in nutans is subject to great va- 

 riations and appears to be dependent to a great extent on temperature. 

 The autumnal rosettes have many reddish spots, appearing in leaves 

 which were devoid of them during the summer, as well as being present 

 in the young autumn leaves in an early stage of their growth. During 

 the spring of 1912, which was quite warm during the latter part of 

 April and in May, there were few or no red spots on the stem leaves 

 of nutans. On the other hand, the spring of 1914 was cold during the 

 same period. The stem leaves had formed during this period numerous 

 roundish, red spots, so that the plants up to 3 decimeters high presented 

 a very peculiar aspect for the species particularly as the young leaves 

 were somewhat narrower than normal for this species. The aspect of 

 the stem leaves due to these two characters was so strikingly different 

 from the normal, that it raised the question in my mind as to whether 

 or not the species was changing. However, from observations on the 

 appearance of red spots on the autumnal rosettes in relation to the 

 coldness of the season, I felt confident that the abnormal spotting of 

 the leaves was due to the lower temperature. The narrower width of 

 the leaves (for nutans) was also attributed to the coldness of the season 

 and the younger age. This interpretation of the influence of environ- 

 ment on the spotting and narrowing of the stem leaves appears to be 

 justified, for, in June, with the appearance of warmer weather the new 

 leaves on the stem developed to their normal width and were free from 



