The Meeting of the British Association at York. 187 
heterothallic character respectively of various mycelia. It will be 
remembered that the terms in question were introduced to 
characterise the striking sexual behaviour of these fungi, some of 
which not only refuse to conjugate with hyphae from the same 
mycelium but will only conjugate with those from certain other 
mycelia. These types are known as heterothallic. 
The author also contributed a general paper (which will be 
found in the September number of the Botanical Gazette), on 
“ Differentiation of sex in thallus, gametophyte and sporophyte.” 
In the last case the words heterophytic and homophytic are used. 
Thus Aspidium is homophytic, homosporangic and homothallic, 
Selaginella homophytic heterosporangic and heterothallic, Populus 
heterophytic, heterosporangic and heterothallic. Investigations are 
now proceeding on sexual differentiation in the sporogonium of 
Bryophytes. It is found that if all the spores from a Marchantia 
sporogonium are sown together they produce a mixed crop of male 
and female plants and the effect of conditions cannot alter this 
result. It is therefore to be supposed that segregation of sex must 
take place during the development of the spores. Dr. Lang, Mr. 
V. H. Blackman and Mr. Gregory took part in the discussion on 
these papers. 
Of purely physiological papers, Professor Bottomley contributed 
a very interesting account of his successful attempt to inoculate 
papilionaceous plants with the root-nodule organisms belonging to 
non-papilionaceous Leguminosae and to plants of quite different 
families, those of Acacia (Mimoseae) and of Elaeagnus and Alnus 
being chosen. In another paper, Professor Bottomley showed 
that the long known effort of sprinkling urine on the floors of 
greenhouses in order to cause a more luxuriant growth of orchids 
is due to the presence of both nitrite and nitrate bacteria in the 
cells of the velamen, which are thus able to utilise the ammonia 
arising by decomposition of the urine and absorbed along with the 
water vapour normally condensed by the velamen. 
Miss C. B. Sanders, of Oxford, described some experiments 
carried out in Professor Gotch’s laboratory on the local production 
of heat connected with the disappearance of starch in the 
spadices of various Araceae. Her method differed from the older 
investigations of Kraus and Garreau on the same subject by the use 
of Dr. Haldane’s method of simultaneous estimation of oxygen 
and CO„. Remarks on the subject of this paper were made by 
Dr. F. F. Blackman. 
Dr. Ellis, of Glasgow, described experiments to show that 
