October i8, 1900] 



NATURE 



613 



by the very different appearance of sacs in which polar fusion 

 is taking place. The male generative nuclei, when first set 

 free in the embryo-sac, are extremely small and heavily stained. 

 Their chromatic substance is so densely aggregated as to render 

 the spermatozoid to all appearance homogeneous. Of the two 

 spermatozoids one passes to the middle of the sac and there 

 fertilises the definitive nucleus ; the other fertilises the nucleus 

 of the oosphere. By the time the male generative nucleus or 

 spermatozoid has reached the definitive nucleus, it has enlarged 

 immensely, and shows a light spongy structure with scattered 

 chromatin granules. The other spermatozoid increases very 

 little in size, and always remains dark and dense. 



When the spermatozoids leave the pollen-tube they are 

 somewhat short and thick, and only slightly curved, but when 

 the one has approached the definitive nucleus, it has the typical 

 vermiform shape, with one or several coils. 



Thaliophyta. 



Germination of the zoospore in Laminariaceae, by J. Lloyd 

 Williams. The zoospore comes to rest and becomes spherical. 

 The single chloroplast divides in two. A tube is produced, the 

 spore-contents pass into it. At the end of the tube a swelling is 

 formed, into which the contents migrate and are shut off from 

 the empty spore-case and lube by a wall. This has been wrongly 

 described by Areschoug in the case of Dictyosiphon as an in- 

 stance of sexual fusion. In the enlargement, the chloroplasts 

 multiply, and additional eyespots appear on several, which, 

 however, disappear after a few days. The newly-separated cell 

 now divides, and forms a branched protonema-like structure. 



Notes on Dictyola, by J. Lloyd Williams. The factors con- 

 cerned in the production of the fortnightly crops of sexual cells 

 were discussed. Experiments on the liberation of antherozoids 

 show the importance of bright light and cool temperatjure. 

 Dictyota is particularly responsive to changes in the environ- 

 ment. 



The nuclear changes in the unfertilised eggs are peculiar. 

 The chromosomes are differentiated, a very irregular multipolar 

 spindle is formed ; this separates into a number of nuclei of 

 various sizes, in which at first the chromosomes are scattered. 

 These soon disappear, the nucleoli are formed, and the nuclei 

 appear in the resting condition. 



The Azygospores of Entomophthora gloeospora, by Prof. Vuil- 

 lemin (Nancy) (communicated by Prof. Hartog). The genus 

 Entomophthora, as seen in the two species E. Delpiniana and 

 E. gloeospora, shows an intermediate condition between Basidio- 

 bolus, with its uninucleated segments, and Empusa, with its 

 continuous hyphse with scattered nuclei. The resting-spores of 

 Entomophthora may be terminal, lateral or intercalary. The 

 youngest spores contain a single nucleus, which undergoes a 

 series of four successive binary divisions until there are sixteen ; 

 there may, however, be irregularities as regards the number of 

 spores. In the next stage the nuclei approach so as to form 

 eight pairs, and the two nuclei of each pair then fuse ; this 

 fusion is repeated until there are only two left. These last two 

 may then fuse at once, so as to leave the now maturing azygo- 

 spore with a single nucleus, or they may remain apart. This 

 manner of development is interpreted as a case of true apogamy, 

 and regarded as corresponding to the sexual process in Basidio- 

 bolus. 



Fungi found in Ceylon growing upon scale-insects (Coccidae 

 and Aleurodidae), by J. Parkin. Fungi associated with scale- 

 insects have till recently been little studied. A few species 

 have been mentioned from time to time as growing upon scales 

 of dead coccids, but, till within the last few years, hardly any 

 attention has been called to their probable parasitic character, or 

 to the possibility of their being employed to check the ravages of 

 scale-pests. Webber in 1897 pointed out for the first time the 

 parasitic habit of certain species — five in all —of Aschersonia on 

 scale-insects infesting the orange and other plants in Florida. 

 Zimmermann (Java) in the following year gave a preliminary 

 account of a fungus (Cephalosporium) attacking the green bug 

 (Lecanium viride), so harmful to the coffee, and described how 

 it may be artificially cultivated for infecting experiments. 



The various kinds dealt with were referred to the following 

 genera : — Nectria, Torrubiella, Aschersonia, Cephalosporium, 

 Verticilliuni, Microcera, Campsotrichum (?). 



Mr. Parkin drew attention to the wide distribution, especially 

 in and near the tropics, of fungi infecting scale-insects, and re- 

 ferred to them as the true cause of death of the insects. The 



NO. 1616, VOL. 62] 



paper was illustrated by a series of carefully-prepared specimens 

 and drawings. 



On the life-history of Acrospeira mirabilis (Berk, and Br.), 

 by R. II. Biffen. Loose brown masses of the spores of this 

 fungus are occasionally found in Spanish chestnuts. These 

 spores are developed from the apices of hyphae coiled into a 

 spiral of, at the most, two turns, which becomes septate into 

 three cells ; the cell next below the apical one swells and hiecomes 

 thick-walled, thus forming a chlamydospore. The coiled hypha 

 may also develop into a spiral resembling the ascogonium of 

 Eurotium, which, after investment by branches arising from its 

 apex, breaks down into chlamydospores. In this way bodies 

 very suggestive of the spore-masses of some of the UstilagineJE 

 are formed. Endoconidia are found in old cultures. Some 

 evidence has also been obtained for the existence of an ascigerous 

 stage. ^ 



On the structure of the root-nodules of Alnus glutindfUz^y 

 T. W. Woodhead. The nodules are traversed by a central 

 strand of short, thick-walled fibres, with transverse pits in the 

 walls. Surrounding this are 4-5 layers of cubical cells, rich 

 in protoplasm, followed by a small-celled bulky cortex. On 

 the outside of this is a phellogen, which produces a layer of 

 cork several cells deep. The cortical cells are largely occupied 

 by the organism which produces the nodule. 



The organism is usually present as a globular sporangium at 

 the end of a short hypha. Towards the base of the nodule are 

 strands of cells occupied by disorganised contents indicating a 

 previous tract of growth of the organism : this is succeeded by 

 groups of cells filled with the organism in various stages. To- 

 wards the apex, and immediately behind the growing-point, the 

 cells containing the sporangia are immediately followed by cells 

 filled with fine hyphal filaments, which may be seen to penetrate 

 the walls of the young adjacent cells. 



A Gymnosporangium from China, by Prof. F. E. Weiss. This-- 

 fungus was first observed by Dr. A. G. Parrott in the spring of 

 1899 in Lao-ho-kou, in North Central China. Its spore masses., 

 made the'r appearance in April after a few days' continuous rain 

 on the branches of Juniperus chinensis in the form of bright 

 yellow, gelatinous masses. The teleutospores are of the usual 

 type, two-celled, tapering towards both ends and somewhat 

 rounded at the apex. They possess eight germ-pores. What is 

 in all probability the Roestelia stage of this fungus was observed 

 during the summer on the leaves of the pear, Pyrus sinensis^ 

 Ldl. A tree of this species growing in proximity to the infected i 

 junipers was attacked by a fungus of the Roestelia type» 

 producing typical aecidiospores. 



In the appearance of its teleutospore masses this fungus; 

 appears most nearly related to Gymnosporangium Sabinae 

 (Dicks), a widely distributed form occurring in Europe and in 

 America, and to Gymnosporangium Cunningharnianum (Bar- 

 clay), a Himalayan form, both of which have their Roestelia 

 stage on a pear. 



The biology and cytology of Pythium, by Prof. Trow. The 

 species described by the author was cultivated from conidia and 

 oospores found in rotten cress seedlings. The study of pure 

 cultures led to the following among other conclusions : — ( i ) No^ 

 zoospores are produced under any circumstances. (2) The 

 species is new and ranks as the most highly developed of the 

 genus. (3) The fertilisation-tube penetrates the wall of the- 

 oogonium at a spot prepared for it, passes through the peri-- 

 plasm and penetrates deeply into the egg. One male nucleus, 

 passes down the tube and enters the egg. The oosphere clothes 

 itself with a delicate wall and increases in size. (4) The fusion 

 of the male and female nuclei is delayed until a thick oospore 

 wall has been developed. (5) The nuclei multiply by indirect 

 division in the mycelium and .sexual organs. The only nuclear 

 fusion is that of the male and female nuclei in fertilisation. 



Observations on Pythium, by M. Poirault and E. J. Butler. 

 The authors examined seven species, two of which were unde- 

 scribed forms. In two species, Pythium gracile and P. inter- 

 medium, sexual organs were observed for the first time. Klebs' 

 results on the dependence of spore-formation in Saprolegnia on, 

 external conditions were carried a step further, it being shown 

 that a given spore could be induced to develop zoospores or 

 vegetative hyphre on appropriate treatment. The authors con- 

 clude that ^Mj'mw represents a stage in the colonisation of the 

 land, by saprolegniaceous ancestors resembling Aphanomyces. 

 It is closely linked to the Peronosporaceae through Pythium 

 intermedium, which possesses chains of gonidia, suckers, and a 

 thick-walled mycelium. 



