Are. 
587 
Further Experiments and Histological Investigations on Intu- 
mescences, with some Observations on Nuclear Division in 
Pathological Tissues. 
By Miss ELIZABETH DALE. 
(Communicated by Professor H. Marshall Ward, F.R.S. Received March 18,— 
Read April 6, 1905.) 
(Abstract. ) 
This paper is the third of a series on intumescences. 
The first was mainly anatomical, the second chiefly experimental, and 
beth related to one species, viz. Hibiscus vitifolius. The present paper 
contains (1) an account of further experiments with different plants, chiefly 
with Solanum tuberosum and Populus tremula. On the potato plant intu- 
mescences were obtained experimentally in about 24 hours, either on a 
complete and uninjured plant, or on single leaves, or on small fragments 
of leaves. As in the case of Hibiscus vitifolius, the effect of varying degrees 
of temperature and illumination were investigated, and also the influence 
of nutritive solutions on floating leaves—the constant factor being a 
saturated atmosphere. A close connection was established on experimental, 
developmental, and cytological grounds between intumescences and wound- 
callus. 
(2) Additional anatomical observations were made, and a classification 
of various types of intumescences, based on development and anatomical 
characters, has been drawn up. The cell contents of intumescences on 
various plants have been examined and compared with a view to discovering 
the osmotic substance which causes the initial accumulation of water in the 
formation of intumescences. 
(3) In this connection experiments were made to determine whether the 
relative amounts of acids and salts, respectively, differed in plants with 
intumescences as compared with healthy individuals. 
(4) These observations and experiments, taken in connection with various 
theoretical considerations, led to the conclusion that the actively osmotic 
substance is an acid, probably oxalic acid. They further, as do the experi- 
ments with fragments of leaves, show conclusively that the internal causes 
of the formation of intumescences are extremely local, and that root pressure 
is in no way concerned with the process. 
The results obtained confirm and extend the conclusions reached by the 
earlier work with Aibiscus vitifolius, viz., that moist air, heat, light, and 
