NOVEMBER 5, 1903] 
NATURE 19 
plants, one of which, Pyrola rotundifolia, var. maritima, 
is found in certain parts in great profusion. 
Of the numerous other papers communicated to the 
section, reference can only be made to some of the more 
important. 
Fungi.—Mr. B. T. P. Barker (Cambridge) gave an 
account of the ascocarp in Ryparobius. The ascogonium 
appears to be uninucleate at first, and immediately after 
contact with the antheridial branch contains two nuclei, 
either situated closely together or apparently fusing. Later 
most of the cells of the system of hyphz, developed from the 
ascogonium, are uninucleate, but some contain two nuclei, 
which probably fuse and become the single nucleus of a 
young ascus. Associated closely with this single nucleus 
is a structure of variable shape which has almost as strong 
an affinity for stains as the chromatin of the nucleus itself. 
It appears to be of the nature of a vacuole and to be in- 
timately concerned with the nutrition of the nucleus, which 
at this time is of a remarkably large size. The results 
obtained point to a close relationship between the genera 
Ryparobius and Thelebolus. 
Mr. E. S. Salmon communicated the results of culture 
experiments with biologic forms of the Erysiphaceze, which 
prove that under certain conditions a ‘‘ biologic form ”’ 
which in nature is restricted to the species of a certain 
genus of host-plants becomes capable of infecting species 
belonging to another genus, and species of plants which 
are immune in nature are able to be infected. The author 
considers that it is possible that in this change of infection- 
powers of biologic forms of parasitic fungi in consequence 
of injury to the host-plant an explanation may be found of 
the sudden appearance of disease on plants hitherto immune. 
Prof. H. Marshall Ward, F.R.S., in a paper on Eriksson’s 
mycoplasm hypothesis, showed by means of a series of 
microphotographs and drawings that this so-called myco- 
plasm consists of haustoria only, and that there are no 
grounds for believing that Eriksson’s views are well 
founded. 
Prof. T. Johnson communicated a short note on a willow 
canker which has been the cause of considerable damage 
in an osier holt in the west of Ireland. 
Physiology.—Prof. Letts and Mr. J. S. Totton con- 
tributed a valuable paper on the occurrence of Ulva latissima 
and Enteromorpha compressa in sewage effluents, and on 
variations in the composition of the tissues of these and 
allied seaweeds. The view expressed by one of the authors 
in conjunction with another chemist, that the growth of 
Ulva latissima in quantity in a given locality is a sign of 
sewage pollution, has received remarkable confirmation by 
the occurrence of this seaweed and of Enteromorpha com- 
pressa in the Belfast sewage beds. The spores probably 
found their way into the sewage by leakage of sea water 
into the system. The percentage of nitrogen was found to 
be higher, especially in Enteromorpha, in the sewage speci- 
mens than in those taken from the sea or brackish water. 
Mr. R. H. Yapp gave an account of his observations on 
fruit-dispersal in Adenostemma viscosum. This plant is a 
composite which is widely distributed in the warmer regions 
of the globe. The distribution of the fruit is-brought about 
by a pappus which consists of stalked glands, composed of 
numerous capitate hairs, which secrete a copious viscid fluid. 
The movements of the pappus setz are effected by a group 
of motor cells which forms a pulyinus at the base of the 
stalk of each gland. 
Mr. Harold Wager described some experiments on the 
staminal hairs of Tradescantia virginica, from which it 
appears that the protoplasmic movement can continue for 
some days after the hairs are removed from the plant, even 
if they are completely embedded in vaseline. The author 
also described a method by which the nucleus of the cells 
can be stained by means of the coloured cap contained in 
the vacuole. 
Mr. J. Parkin gave an account of his work on the 
localisation of anthocyan -in foliage leaves. In young 
leaves, and in the autumn coloured leaves, the anthocyan is 
usually confined to the mesophyll; in mature leaves mainly 
to the epidermis, except when the colouring matter is only 
produced under exceptional conditions, when it is usually 
found in the mesophyll. The author concludes that the 
presence of anthocyan in the mesophyll seems to weaken 
somewhat the view that its function is to protect the chloro- 
phyll by absorbing the destructive solar rays. 
NO. 1775, VOL. 69] 
Anatomy and Cytology.—Miss Ethel Sargant and Miss 
Agnes Robertson read a paper on some anatomical features 
of the scutellum of Zea Mais. ‘They find that the epithelium 
of the scutellum in contact with the endosperm. becomes 
folded into a number of gland-like structures in which 
traces of some kind of secretion are commonly found. 
Mr. Arthur W. Hill (Cambridge), in a paper on the 
histology of the sieve tubes of Angiosperms, showed that 
the sieve plates of the mature sieve tubes are traversed by 
relatively thick slime strings, each being enclosed in a 
callus rod. In the radial and tangential walls the slime 
strings, which are grouped into oval or rounded pitted areas, 
are much smaller than those in the sieve plates, and some 
three to six strings are enclosed in a callus rod. Connect- 
ing threads also occur between the sieve tubes and com- 
panion cells. Between the sieve tubes and cambiform cells, 
and between the latter and the companion cells, the small 
groups of threads are found in small and deep pits. 
Mr. J. Lloyd Williams (Bangor) read a paper on the 
alternation of generations in the Dictyotacez and _ the 
cytology of the asexual generation, in which he pointed out 
that the nuclei of the tetraspore plants have about thirty-two 
chromosomes, and that in the formation of the tetraspores 
these become reduced to sixteen. The sexual plants also 
have the reduced number. The evidence, therefore, shows 
that the tetraspore produces a sexual plant, whilst the 
oospore produces the tetraspore generation. 
Mr. L. A. Boodle (London) communicated a short paper 
on the structure of leaves of bracken from different habitats. 
In a very exposed and sunny situation the leaves are hard 
and short, while in a well sheltered and shaded locality 
they are much larger and soft. Long sori and short sori 
are typical of the first and second situation respectively. 
The internal structure of the pinnules varies with the 
habitat in a corresponding manner; the presence of a con- 
tinuous, or nearly continuous, hypoderm and the large 
amount of the palisade tissue formed distinguish the leaf 
of the exposed from that of the sheltered plant. 
Ecology, Distribution, @»c.—In addition to Dr. Darbi- 
shire’s paper on the sandhills of Southport, several other 
papers of some interest were read in this section. Miss 
M. C. Stopes gave an account of the colonisation of a dried 
river-bed. The stream became dried up in April, 1901, and 
during the years 1901-1903 observations were made upon 
the plants found growing on the dried up mud. In 1903 
these included eleven frequent semi-aquatics, of which four 
are locally dominant, and thirty-two frequent land plants, 
of which eight are locally dominant. 
Mr. YT. W. Woodhead (Huddersfield) described his 
methods of mapping the distribution of plants, and the 
anatomical variations produced in the leaves of certain 
plants grown under varying conditions in different plant 
societies. _ He showed clearly by means of photographs 
what striking variations may be produced in the under- 
growth of a wood owing to the nature of the trees immedi- 
ately above it. 
Dr. F. F. Blackman (Cambridge) gave an excellent 
summary of modern views on the phylogeny of the Algz, 
illustrated by diagrams. 
Mr. A. W. Hill (Cambridge) gave an account of his 
recent expedition to Upper Peru, and Mr. W. Wilson com- 
municated a list of some of the plants growing on the 
serpentine rocks of the north-east of Scotland. 
Fossil Plants.—There were only two papers of any im- 
portance in this section. Mr. E. A. Newell Arber (Cam- 
bridge) communicated some interesting observations on 
homceomorphy among fossil plants. Among recent plants 
species of different descent may possess many closely 
identical characters as the result of adaptation to particular 
conditions of the environment. There is some reason to 
believe that similar cases may be found among fossil plants, 
and the author finds some ten genera and species in which 
this phenomenon occurs. 
Mr. Seward communicated a paper by Dr. D. H. Scott, 
F.R.S., and Prof. F. W. Oliver on the seed of Lygino- 
dendron, which was illustrated by some beautiful lantern 
slides. 
Economic Botany.—Mr. E. T. Scammell read a paper on 
the forest resources of Australia available for British com- 
merce. The forest areas of Australia comprise 107,037,000 
acres of marketable timber, or nearly half the areas of the 
forest lands of Europe, excluding Russia. The timbers are 
