September 26, 1907] 



NA TURE 



557 



that the spermatium of the Florideae, and no doubt of the 

 Ascomycetes, was closely related to a freed antheridium. 

 He suggested the existence of a further analogy in con- 

 nection with the events %vhich follow fertilisation. In 

 Ascomycetes a second nuclear fusion takes place in the 

 ascus ; in the Floridea; cell fusions occur, but the nuclei 

 are indifferent or repelled. The cases described by Miss 

 Eraser in which ascus nuclei continued their development 

 without fusion might be regarded as intermediate. Prof. 

 Farmer emphasised the dual aspect of nuclear fusion ; the 

 process was not primarily originated to associate paternal 

 and maternal characters, but possessed a deep physio- 

 logical significance. 



Prof. Blackman also accepted the theory put forward 

 as to the phylogeny of the male organ. He regarded the 

 variety of female organs among Ascomycetes as diflicult 

 to reconcile with their monophyletic origin. The occur- 

 rence of both ccenocytic and uninucleate structures was a 

 specially difficult point. With regard to the sexuality of 

 the Ascomycetes, a fairly complete series now existed, in- 

 cluding Pyronema (Harper, iqoo) and other forms with 

 normal fertilisation ; Lachnea (Fraser, 1907) and Humaria 

 grantdata (Blackman and Fraser, 1906), where the nuclei 

 of the ascogonium fuse in pairs ; Ascobolus, where fusion 

 is probably between a female and a vegetative nucleus ; 

 and Humaria rutilans, where sexual organs are lacking 

 and the vegetative nuclei fuse. Prof. Farmer, in a recent 

 paper, had grouped such various forms of reduction under 

 the general term pseudapoQamy, but Prof. Blackman felt 

 that a more detailed classification was required. A further 

 stage would be that in which no fusion took place, and 

 one would then expect a corresponding difference in the 

 divisions in the ascus. 



Prof. Blackman accentuated the importance of Humaria 

 rutilans as the first case in which the behaviour of the 

 chromosomes in asexual fusions had been elucidated, and 

 dealt with the difference between synaptic and non- 

 synaptic reduction, associating the latter with the fusion 

 of undifferentiated nuclei. In Humaria there is no physio- 

 logical difference between the two fusions, but the first 

 is obviously the relic of a normal fertilisation. He re- 

 garded the definition of a sexual fusion as dependent on 

 the origin of the process, and not on the subsequent 

 behaviour of the nucleus. 



Prof. Hartog considered the attempt to differentiate 

 between fusions of sexual and of vegetative nuclei in the 

 ascogonium as puerile, since the pronuclei lose their dis- 

 tinctive sexual characteristics before fusion. He pointed 

 out that brachymeiosis differs from other known types of 

 division in that a sorting, but no splitting, of the chromo- 

 somes takes place, and referred to the unexplained fusions 

 of three gametes in the Volvocineae. 



Dr. Darbishire spoke of the complex structure of the 

 multicellular ascos'onia of Lichens, and Prof. Buller sug- 

 gested that a studv of the nhenomena of spore distribution 

 mi^ht throw light on the phvlogenv of the .Ascomvcetes. 



Miss Fraser, in replying, dealt with various points raised 

 during the discussion, and pointed out that the diflficultv 

 of relating coeno'-vtic with uninucleate forms was lessened 

 by the occurrence of both states in the scolecite of 

 .Ascobolus. 



Physiological Papers. 



Prof. H. E. Armstrong read a paper by Dr. E. F. 

 .\rmstrong and himself on " Enzymes, their Mode of 

 Action and Function," which, it is understood, will shortly 

 be published in the Annals of Botany. The authors 

 pointed out that the distinctive feature of the chemical 

 changes gomg on in the bodies of organisms was the fact 

 that they are under the control of the action of the bodies 

 called enzymes. Great progress had been made in our 

 knowledge and activity of these bodies within recent years, 

 one of the outstanding conclusions being that all chemical 

 equations involving their action are to be written as re- 

 versible changes. It has for a long time been usual to think 

 of ferment action as mainly concerned with destructive 

 mr^iabolic action, but it is probable that the constructive 

 aciivity of enzymes is really far more important biologically. 

 '1 ho authors illustrated the probable structural relations of 

 enzymes to. the organic substances upon which they act 

 liv reference to the structural formulas of various sugars, 

 showing that when a given enzyme can act upon several 



different substances it is because it can work upon a group 

 of atoms common to all these, and in each case holding 

 together the other groups. In the case of albuminoids a 

 complex enzyme is required, but the conception of a 

 skeleton which can only be packed with atoms in a par- 

 ticular way enables us to see that it is unnecessary to 

 assume a mechanism so complex as the structure that has 

 to be produced. It is probable that we should conceive 

 of the constructive activity of enzymes in this way — that 

 the enzyme is a skeleton on which the complicated organic 

 body can be built up. Dr. E. F. Armstrong replied to 

 some questions put by Prof. Reynolds Green and others. 



Prof. Bottomley communicated some results of his 

 experiments on the inoculation of nitrogen-fixing bacteria 

 in plants other than the Leguminosoe, and stated that 

 tomatoes had been made to produce a greatly increased 

 crop by this means, the bacteria having been first culti- 

 vated in tomato-juice ; in wheat the bacteria had been 

 induced to establish themselves in the cortex of the 

 root, though no nodules like those on the roots of 

 Leguminos^ are formed. The economic possibilities of 

 these results, if capable of further development, are 

 sufficiently obvious. Prof. Farmer remarked that this was 

 a case in which we ought to have concluded that if the 

 organism could be cultivated outside the plant it could 

 be got to live upon other plant-cells containing carbo- 

 hydrates. It had been shown that rusts could be induced 

 to live on different hosts by special training. It was 

 known that wheat can go on for an unlimited number of 

 years producing about thirteen bushels In the acre, but 

 this would probably be much exceeded without manuring 

 if the wheat plants, by the aid of these bacteria, were 

 enabled to fix atmospheric nitrogen. 



Mr. F. Darwin read a paper on the cotyledon of 

 Sorghum as a sense organ. It was directed towards con- 

 firming the belief that the cotyledon is the seat of geo- 

 tropic sensitiveness, evidence for which was given in a 

 paper read before Section K at Dover (iSqq), and published 

 in the .4nnals of Botany. The results given in the present 

 paper were obtained partly by Czapek's " glass-boot " 

 method and partly by an adaptation of Piccard's centri- 

 fugal method. The conclusions, though not perhaps 

 finally convincing, are strongly in favour of the view that 

 the cotyledon is the geosensitive region. The paper also 

 contains observations on the traumatic and heliotropic 

 curvatures of Sorghum. 



Morphological Papt-rs on Ptcridophytcs and 

 Ptcridosperms. 



Prof. Bower read a paper on the embryology of Pterido- 

 phytes, embodying the result of his recent work on this 

 subject. He pointed out that there are two types of 

 pteridophytic embryo : — (i) the Lycopod type, w'hich agreed 

 with the Bryophytes in having a suspensor ; and (2) the 

 fern type, in which there is no suspensor. The main 

 point he wished to bring out w^as that there is a definite 

 polarity in the embryo defined at once by the first segment- 

 ation, the centre of the " epibasal segment " forming one 

 pole coinciding with the stem apex. On the other hand, 

 the polarity of the embryo with regard to the axis of the 

 archegonlum is quite variable, as is the number and 

 time of origin of the first leaves and roots, and also of 

 the haustoria and protocorms. In Isoetes there is no 

 suspensor; the initiation of the polarity is changed, and 

 is even variable within the species. The embryo of 

 Isoetes is inverted as compared with an ordinary Lycopod 

 embryo, but is otherwise in line with the other Lycopods. 

 The initial polarity of Botrychium obliquum, according to 

 Lyon's account, is also exactly inverted as compared 

 with Ophioglossum. Goebel's position, that the organs of 

 a plant are laid down in the most suitable positions 

 according to circumstances, is not confirmed by the study 

 of embryos. .After the first segmentation the polarity is 

 definitely fixed. There was an interesting discussion, in 

 which Dr. Scott, Prof. Oliver, Prof. Weiss, and Mr. 

 Worsdell joined, and which displayed a general agreement 

 with the author's conclusions. 



Mr. Gwynne-\'aughan contributed a striking paper on 

 the real nature of the so-called tracheids of ferns. The 

 author was led by some observations on fossil 

 Osmundacea? to investigate the pitting of the xylem 



NO. 1978, VOL. 76] 



