106 



KNOWLEDGE. 



March. 1911. 



NITROGENOUS SALTS IN SKAW.ATER.— Gebbing 

 {Iiitcniaf. Rcviic d.gcs. Hydrubiol. ittid Hydrogr., 19101 has 

 collected the results of the German South Polar Expedition with 

 reference to the^iitrogen-content of sea-water, comparing these 

 results with others previously obtained. Although chemical 

 in character, Gebbing's paper is of great interest in connection 

 with the distribution and periodicity of the plankton or surface- 

 living vegetation of the sea. The chief results are the 

 following. The content of the ocean in ammonium salts is 

 fairly constant, the average value being 0-05 milligrams per 

 litre. The distribution of the nitrates and nitrites is, however, 

 very variable, the highest proportion of these salts in the surface 

 water being found in the Antarctic Ocean, while it dwindles 

 towards the Equator from 0-5 milligrams to 0-1 milligrams 

 per litre. In the North Atlantic and in the North Sea there is 

 marked poverty in these salts, as compared with the Southern 

 Hemisphere, there being practically no increase on passing 

 northwards from the Equator. The scanty plankton of tropical 

 seas is probably due to the fact that the higher temperature 

 favours the growth of denitrifying bacteria, which attack 

 nitrates and nitrites, setting free nitrogen. At the Equator, 

 also, there is a much more rapid falling-off in nitrogen-content 

 in passing below the surface, and this may obviously be 

 attributed to the greater vertical circulation of the water in the 

 Tropics. Gebbing's interesting memoir is an important 

 contribution to biology as well as to chemistry and oceano- 

 graphy, and helps in clearing up various problems in the 

 distribution of the floating vegetable population of the sea. 

 which is largely used as food by the animal plankton as well as 

 by the larger denizens of the ocean, 



CYCAD ROOT-TUBERCLES,— The remarkable coralloid 

 roots of Cycas have long been known to harbour colonies of 

 the Blue-green Alga Nostoc or Aiiahacna, which usually 

 form a definite layer in the cortex of these roots. In addition 

 to the Nostoc, bacteria occur in these roots, evidently causing 

 the formation of the tubercles and living in symbiosis with the 

 Alga. :\n interesting pap.:r on this symbiosis was read b\- 

 Professor Bottomley at the Sheffield Meeting of the British 

 Association (see Botany Notes in " Knowledge." October, 

 1910) ; the presence of the bacteria was noted by Schneider 

 in 1894 [Bot. Gaz.). Now, Zach iOesten: Hot. Zeitschr., 

 19101 has found that in addition to the Nostoc and the 

 bacteria, these Cycad roots contain a fungus which attacks 

 the cortex cells and causes degeneration of the nuclei, loss of 

 starch and production of calcium oxalate in the infected cells. 

 No fungus filaments occur, however, in the Nostoc zone, and 

 Zach found that the fungus has nothing to do with the 

 causation of the tubers, but li\es in the roots simply as parasite, 



RECENT WORK ON THE LOWER FUNGI.— Among 

 many interesting papers on the lower Fungi, there are some 

 which serve to link up the Yeasts to the more typical lower 

 .■\sconiycetes. The Yeasts have long been regarded as 

 degenerate Ascomycetes, their peculiar features — such as the 

 budding process of multiplication and the general absence of 

 sexual fusion — being correlated with their mode of life in 

 sugar solutions, which they decompose with the formation of 

 alcohol and carbon dioxide. The work of Hansen and others 

 has shown that not all Yeast species cause alcoholic fermenta- 

 tion, and that some species produce a definite, though simple, 

 mycelium or filamentous plant-body, while the spores of some 

 species have a peculiar hemispherical or hat-like form, which 

 agrees exactly with the shape of the spores in Eiidomyccs. 

 Barker's interesting discovery of the conjugating Y'easts, in 

 which the cells fuse in pairs before producing spores, may be 

 regarded as an indication of a simple sexual process similar 

 to that observed in such simple Ascomycetes as Erciiiascus 

 and Gymiioasciis. 



Guilliermond {Rev. gen. Bot., 1909) has investigated 

 the following forms of lower Ascomycetes: — Eranascus. 

 Endomyces, Saccliaroiuycopsis. In Ereniasciis the cells 

 of the mycelium are at first multinucleate, but later become 

 uninucleate, and the asci arise in most cases from two fused 

 cells, but sometimes without fusion (parthenogenesis). In 

 fusion, a nucleus from each of the two cells migrates into tlu' 



young ascus, the two nuclei fuse, and the fusion-nucleus 

 di% ides until the eight spore-nuclei are formed. In Eitdomyces 

 fibiiUger the mycelium, when in sugary liquids, forms buds 

 exactly like those of Yeast, and multiplies rapidly in this way. 

 In a paper which appeared simultaneously with that of 

 Guilliermond. Dombrowski [Coiiiptcs reiidits dii lab. dc 

 Carlsbcrg, 1909) showed that these Yeast-like cells of E. 

 fibnUgcr can produce conidia. differing from the sprouting 

 Yeast-like cells themselves in being able to resist heating to 

 55' C, a temperature which destroys the budding cells, 

 Guilliermond found that, as a rule, the asci arise singly as 

 branches from the ordinary mycelium, showing no trace of a 

 fertilisation process, and producing only four spores. In some 

 cases, however, anastomoses occur between the ascus 

 mother-cell and the neighbouring mycelium cell, or between 

 an ascus mother-cell and a Yeast-like cell, and this he thinks 

 points to degeneration of a former fertilisation. In Eiidviuyccs 

 mngnnsii the asci may either arise parthenogenetically, or 

 after conjugation of two mycelial branches differing in size, 

 four spores being formed ; in this species no Yeast-like budding 

 occurs, though resting cells are formed, InSaccharoinycopsIs, 

 there is no trace of fertilisation : the ascus contains four 

 spores; according to the culture conditions the plant 

 produces either a mycelium or Yeast-like cells, and the genus 

 is closely related to Eiidomyccs. being distinguished from 

 the Yeasts tSacchari)iuycctes) by the double wall of the 

 spore. Guilliermond concludes with a discussion of the 

 systematic arrangement and inter-relationships of the lower 

 Ascomycetes. pointing out that in Erciiiascus the only method 

 of reproduction is the formation of an ascus from two fused 

 cells, while in Eiidomyccs the asci may be formed either by 

 fertilisation or by parthenogenes. is and in addition to asco- 

 spores the plant reproduces itself by Yeast-like budding and by 

 conidia. The genus Eiidomyccs forms a transition from 

 Erciiiascus to the Yeasts, a form like E. fibuUgcr connecting 

 Ercinasciis to the ordinary Yeasts [Saccliaroiiiyces) and the 

 Conjug'ating Yeast (.^vgos(icc/;(7/'o/)/_vct's), while E. magtiiisii 

 leads to the Splitting Yeast iScliizosaccharomyccs). 



Guillicrniond's important results are confirmed by a paper by 

 Lewis I Maine Agric. E.xp. Sta., Bulletin 178) on a new species 

 of Endomyccs discovered by him on decaying apples. In 

 this fungus — Endomyccs malt — the asci arise by partheno- 

 genesis on short lateral branches of the mycelium and produce 

 four spores, while conidia are also produced, but no Yeast- 

 like budding occurs and the Fungus cannot ferment sugar, 

 though Endomyccs magnusii can do this. 



Westling (Svciisk bot. Tidskr., 1909) has described a new 

 genus. Byssochlamys, which he regards as forming a 

 connecting link between Endomyccs and Gymiioasciis. This 

 Fungus was found on plants that had been preserved in 

 alcohol, and it could not only exist but actually flourish in 

 strong alcohol (90%), which kills even the spores of most 

 other F~ungi ! This new Fungus proved even more long- 

 suffei'ing under adverse conditions than the ubiquitous and 

 highly-resistant Blue Mould {Peiiicilliiim ), and grew well at 

 37° C, ousting Pcnicilliiiin from a culture heated to this 

 temperature. Byssochlaiiiys reproduces itself by means of 

 ascospores. conidia, and thick-walled resting cells (chlamy- 

 dospores) ; the asci have eight spores and arise laterally from 

 a spirally coiled ascogonium, which is usually fertilised by a 

 male filament (antheridium) but is sometimes parthenogenetic. 



HELIOTROPISM. — Some of the more recent work on 

 heliotropism was summarised in these columns a short time 

 ago. An interesting paper by Figdor {Ann. jard. bot. 

 Buitciizorg) shows that not only do foliage leaves perceive 

 the stimulus of one-sided light but that this stimulus is 

 transmitted backwards to the stem. Figdor experimented with 

 the leaves of Begonia, arranging his apparatus so that onl\- 

 the leaf-blade was exposed to the light, and found that not 

 onlv the leaf-stalk but the stem below the leaf showed strong 

 curvature towards the light. Figdor had previously shown, 

 also in experiments with Begonia, that the stem itself can 

 perceive and respond by curvature to the stimulus of light 

 falling upon it from one side, but his recent result is of 

 great importance in showing that in Dicotyledons, as well as in 



