684 TRANSACTIONS OF SECTION K. 
2. On the Disappearance of certain Cryptogamic Plants from Charnwood 
Forest, Leicestershire, within historic times. By A. R. Horwoop. 
Like some phanerogams formerly found within the boundary of the historic 
Charnwood Forest, Leicestershire, there are many cryptogams which have become 
extinct within the last century. 
Amongst these last the lichens, hepatics, and mosses have received most 
attention from a systematic point of view locally, and the communication referred 
mainly to those plants. 
It may be stated, however, that, as a general rule applying to all the Crypto- 
gamia, certain plants are confined, in the Leicestershire district, to Charnwood 
Forest, From various causes a considerable number have disappeared from that 
region. The principal of these are (a) the drainage and disforestation of the forest, 
and (6) the increased amount of smoke resulting from the ever-growing number 
of colliery and other workings in the neighbourhood, causing the diffusion of 
sulphurous gases, which are detrimental to the growth of plants, affecting 
principally their leaves or vegetative organs. Licheus are especially susceptible 
to this new poisoning agent, and it does not seem to have hitherto been placed 
on record how widespread is the extermination of the lichens of Great Britain. 
As a result, numerous species and genera have become extinct, and many plants 
are found to be imperfectly developed. According to the Rev. H. P. Reader, who 
first pointed out this fact to the author, the approaching disappearance of all but 
the hardiest lichens is not confined to Leicestershire, nor even to the manu- 
facturing districts of Central England, but is noticeable also in the less populated 
portions of the South of England. 
A summary of the cryptogamic plants that have become extinct in Leicester- 
shire was given, which included not only a large number of the rarer and more 
interesting lichens, but a considerable number of species of hepatics and mosses. 
3. On the Cotyledon of Sorghum as a Sense Organ. 
Sy Francis Darwin, F.2.S. 
The observations here given are supplementary to the paper on Geotropism and 
the Localisation of the Sensitive Region read before Section K in 1899 and 
published in the ‘ Annals of Botany,’ vol. xiii. 
The method employed is a modification of Czapek’s well-known experiment on 
roots in which the organ is bent by being allowed to grow into acurved glass tube. 
In my work, the cotyledon of Sorghum is forcibly bent close to the base and fixed 
in that position to a vertical plate of cork. It was found that this treatment 
produces a traumatic eflect on the hypocotyl which tends to curve in the direc- 
tion of the bend impressed on the cotyledon. The seedlings can be fixed in two 
positions: in one (No. 1) the traumatic effect is added to the geotropic stimulus 
which according to my experiments of 1899 originates in the cotyledon; in 
position 2 the traumatic effect and the cotyledonary stimulus are opposed to each 
other. In position 1 the curvature of the hypocotyl is always in the direction 
which would be accounted for if the cotyledon were the sense organ for gravity. 
In position 2 the results were irregular, no doubt owing to the opposition of the 
sraumatic effect. Thisresult is not conclusive, but it should be noted that if the 
teat of geo-perception were exclusively in the hypocotyl the results must have 
been reversed—a curvature should have occurred regularly in position 2, while the 
curvatures should have occurred irregularly in position 1. The conclusion that 
geo-perception occurs in the cotyledon is confirmed by using the method which 
Piccard employed in the case of roots. Sorghum seedlings are fixed by their 
cotyledons to a Knight’s machine (having a horizontal axis) so that the cotyledon 
and hypocotyl are exposed to opposing centrifugal stimuli. his is effected by 
arranging the seedling so that the junction of the cotyledon with the hypocotyl 
} But see a paper read at the Bradford meeting, 1900, by Mr. Albert Wilson, 
dealing with the same question. 
