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JOHN H. EHLERS 
scopically. In other species groups of hyaline cells filled with large 
starch granules were observed more or less regularly. These groups 
usually appeared immediately below the epidermis. No explanation 
is attempted. The author hopes to make this a subject for further 
investigation. 
While no conclusive evidence of starch formation was observed 
after December 13, it does not follow that all photosynthetic activity 
had ceased. Carbohydrates may have been formed and used or trans- 
located as fast as formed. It merely indicates that photosynthesis 
was not sufficiently active under the conditions that obtained during 
January and February to result in the production of starch in the leaf. 
The species examined and the results obtained are as given below. 
No starch : Pinus strohus L. 
More or less starch: 
Juniper us communis L. Thuya occidentalis L. 
Juniperus virginiana L. Picea Abies (L.) Karst. 
Tsuga canadensis (L.) Carr. Ahies halsamea (L.) Mill. 
Starch in groups of hyaline cells: 
Pinus laricio austriaca Endl. Pinus ponderosa Laws. 
Pinus sylvestris L. Pinus Banksiana Lamb. 
These results do not agree with those of Schulz (26) and Lidforss 
(13). The former maintains that the leaves of all gymnosperms 
except the Gnetaceae contain no starch in winter; the latter states 
as a universal rule that all green plant cells are free from starch during 
the winter months. Evidently their results do not hold for southern 
Michigan just as they do not hold for the warmer portions of Japan 
as was shown by Miyake (18). This problem should be given more 
extended investigation. 
V. Summary 
The data presented above show that evergreen conifer leaves, 
even under winter conditions, through the absorption of radiant 
energy, maintain temperatures from 2° to 10° C. higher than the 
surrounding air. The maximum obtained under brilliant illumination 
and with a light breeze blowing was 8.83° C. (Table V). In still air 
the temperature difference is considerably higher. This was shown 
