282 
E J. Salisbury. 
The amount of the conducting tissue has perhaps been too 
much overlooked as a factor in transpiration, for given a constant 
suction force, the rate of flow will be dependent upon the size and 
number of the supplying tracheae. In the present paper some of 
the preliminary results obtained in an investigation of the above 
considerations are given. The work was begun as an outcome of 
the author’s results' in connection with the extrafloral nectaries of 
Polygonum, but owing to the difficulties experienced in finding a 
fully reliable method of estimation and the time involved in obtaining 
a single result the data brought forward are fewer than the author 
would have wished, but it is hoped at a future date to multiply the 
evidence here adduced. Comparatively little work having a direct 
bearing upon this subject has as yet been done. Kohl, 2 working on 
the stems of Hedera helix, Mentha aquation, Thalictrum galioides, 
and other plants shewed that the bundles, as a whole, of plants 
grown in a damp atmosphere were smaller in size than those of 
other plants of the same species grown in a dry atmosphere. Jost 3 
experimenting upon the hean seedling found that removal of a 
cotyledon caused the corresponding bundles to remain rudimentary, 
whilst the severing of an individual strand caused its abortion below, 
though continuing its development above. Schacht 1 had also made 
an observation of interest in this connection namely that in the 
saprophytic Epipogou gmelini the leaves are without stomates, and 
associated with this feature no vascular system is developed. At 
the time of writing, a paper has appeared by Hill and de Fraine 5 in 
which a relation is shewn to exist between the area of cotyledons 
and their vascular supply as a whole. 
From these scattered observations it is at once apparent that 
there is a general relation existing between transpiration and the 
development of vascular tissue. In 1886 Darwin and Phillips 6 
shewed the importance of the cross sectional area of the conducting 
lumina of the vessels by their experiments upon compressed and 
bent stems which exhibited a diminution in the transpiration 
current. 
1 Ann. Bot., Vol. 23, 1909, pp. 229-242. 
2 “Transpiration der Pflanzen,” 1886, p. 116, Pis. II-IV. 
3 “ Ueber Beziehungen zvvischen der Blattentwickelung und der Gefass 
bildungen in der Pflanzen.” Bot. Zeit., Bd. 51, 1893, pp. 85-134. 
4 “ Beitrage zur Anatomie und Phys. der Gewachse,” 1854, p. 115. 
6 “ A consideration of the facts relating to the structure of seedlings.” 
Ann. Bot., Vol. 27, pp. 257 272, 1913. 
6 “ On the transpiration stream in cut branches,” Proc. Comb. Phil. Soc. 
Vol. 5, p. 364. 
