402 Dr, F. F. Blackman and Miss G. L. C. Matthaei. [Apr. 11. 
polypides, and the restriction of the polypides and their buds to separate 
tubes. I propose for it the name Cephalodiscus nigrescens. 
EXPLANATION OF PLATE. 
Photograph of the Natural Size of a Specimen of Cephalodiscus nigrescens, Lankester, 
from the Antarctic Ocean. 

Experimental Researches in Vegetable Assimilation and Respira- 
tion, IV.—A Quantitative Study of Carbon-Dioxide Assim- 
lation and Leaf- Temperature in Natural Illumination. 
By F. Frost BLAcKMAN, D.Sc., Fellow of St. John’s College, Reader in Botany 
in the University of Cambridge, and GABRIELLE L. C. MATTHAE!, B.A., 
Fellow of Newnham College. 
(Communicated by Francis Darwin, For. Sec. R.S. Received April 11,—Read 
April 13, 1905.) 
CONTENTS. 
Page 
Section [.—Introduction. Apparatus and Procedure ...................0000 402 
55 II.—On the Internal Temperature of Leaves exposed to Natural 
Tibamainiation! (2 ior se coeciat nocaent ceeieas meee a aca ee ane 406 
5) LIR Assimilation in Natural lihaminatione.es....4...05 eee 412 
FS IV.—lIllumination and Temperature as “ Limiting Factors” in 
Assim Tati. cahc cede aciseenan ae ence tegen 426 
53 V.—The Photosynthetic Value of Full Insolation ..................... 435 
‘ VU-—tThe Specific Assimilational Characteristics of Diverse Leaves 444 
» WI1.—The Limitation of Assimilation by the Natural Environment 449 
sire, Woe —Comelusion sat o/s coke ie a.cin. eset yal scene kee eet ee Ee ee 456 
Section I.—Jntroduction. Apparatus and Procedure. 
It has been made evident by the experiments recently published by one of 
us,* that the amount of carbon-dioxide assimilation which a leaf is actually 
performing, or is capable of performing, is profoundly affected by the 
temperature of the assimilating cells. 
Neglect of this factor has been a fruitful source of confusion in attempts 
to estimate the effect of different intensities of light upon the process of 
assimilation. 
* “Experimental Researches on Vegetable Assimilation and Respiration. III.—On 
the Effect of Temperature on Carbon-dioxide Assimiiation,” by G. L. C. Matthaei, ‘ Phil. 
Trans.,’ B, vol. 197, 1904; to be referred to as “ Assim. and Resp. ITI.” 
