OCTOBER 8. l8 9 8 - 



GARDENERS' MAGAZINE. 



653 



re a 



HOMOLOGY OF PLANTS. 



By Professor F. O. Bower, D.Sc, F.R.S 



(Continued from page 635. ) 



brief reference must be made to the very beautiful results of 



the changes in the zygote of Cystopus candidus, which have 

 lager rTfied and extended by Berlese. Wager states that in this fungus 

 rpss of fertilisation does not differ in any essential particular from 

 ^cproce ^ ^ ^ takes D i ace i n Angiosperms. On the division of the 



the process Mjttt*^ 

 JbScd 'in the nuclei of the ogonium. 



nucleus of the zygote the number of the chromosomes present 

 n division appears to be considerably in excess of the number 



-r *\*~ ~.\ — c4T} y coun ting as carefully as 



nssi 



e im 



hie twenty to twenty-four, or even more, appear to be present, and 

 oression is produced that the number is certainly much larger than 



— " Divisions of the nucleus then follow to 



that observed in the oogonium • w u aw 



f m four eight, sixteen, and finally thirty-two, in which condition a 

 od of rest ensues ; and, finally, it appears that a division of each into 

 four follows, to form the nuclei of four spores. Wager believes the re- 

 duction to take place at this last division, and Berlese has established a 

 strong probability that such a reduction actually does take place. Plainly 

 these observations are not final or conclusive, and even if they were, the 

 strict homogeny of this fruit-body with a rudimentary sporophyte of a 

 green plant would not be proved. It must, however, rank at least as an 

 iportant parallel case, illustrating how the reduction may be effected in 



a distinct line of descent. 



We see then that in green Algre such as (Edogonium^ Sphccroplea, and 

 CoUochffte certain divisions follow fertilisation, but we are not yet in 

 possession of the nuclear details. I prefer, therefore, to suspend 

 judgment as to the nature of those divisions ; but in view of the 

 peculiar behaviour already seen in other zygotes it may be distinctly 

 anticipated that some form of reduction will be demonstrated at that 

 stage. If that be shown then we shall be right in recognising in these 

 small cell-bodies the rudimentary correlative of a sporophyte — the sort of 

 beginning from which a neutral generation may have sprung in land- 

 living plants. We cannot go farther than this as regards the green Algae 

 until we are in possession of the facts. There is no greater desideratum 

 m morphology at the present moment than a detailed knowledge of the 

 germination of zygotes such as that of CEdogoniuw. 



Here I may remark that the admirable observations of Professor 

 Klebs, whom the Section will welcome as a distinguished guest, do not 

 appear to me to touch this question. His very varied and convincing 

 experiments show in a number of algre and fungi that, as regards the suc- 

 cession of vegetative and sexual modes of propagation, the experimenter 

 has a very complete control. I do not find, however, any observations 

 of his which touch the behaviour of germinating zygotes of green algae as 

 regards details of segmentation. I do not mention this as in the least 

 impairing the brilliancy of Professor Klebs's work, but because Professor 

 Ward has brought Klebs's results to bear upon the discussion on anti- 

 thetic alternation in a manner which I do not think that the facts will 

 support 



II.— Bryophyta. 



Turning now to the bryophytes, these plants stand at the moment in 

 a somewhat discredited position. We have been warned by Dr. Scott 

 that u there is no reason to believe that the Bryophyta, as we know them, 

 were the precursors of the Vascular Cryptogams at all," and that " there 

 is no appreciable resemblance between the fruit of any of the Bryophyta 

 and the plant of any Vascular Cryptogam," and the suggestion has been 

 thrown out afresh that they may really be 11 degenerate descendants of 

 ■gher forms." 



In view of statements such as these it may be well to examine the 

 Bryophyta quite separately, without reference to Vascular Plants at all, 

 ami see what are their main bearings on theories of alternation. And if 

 e bryophytes were the only Archegoniate Plants in the world, I think 

 necase for their origin by a piogressive antithetic alternation would be 

 m uncommonly strong one. The points which are especially noteworthy 

 leou ' ' 1 «e readiness with which they may be arranged in natural 

 ences which illustrate increasing vegetative complexitv of the sporo- 



de^k \\ COnseqUence of P ro S ressiv e sterilisation; (2) the nuclear 

 *ancv f K are aS yet known > however, in only few cases ; (3) the con- 

 seldom H \ alternatin £ phases, the relations of which are very 



disturbed by apospory, and never, to my knowledge, byapogamy. 



todies » T thCSe matters has been dealt with at len S th in m y 

 are th 1S ' ° f course ) possible for anyone to read such sequences 



Plifirpf re m £ nt,oned in reverse order, and to uphold a theory of 

 canon ; but this must be shown to be in accordance with proba- 

 'ow it appears to me that the general probability in the case of 



°fes whirh ' S gainst simplification, for the larger the number of 

 en i n C .J ca ? be matured the greater the probability of survival ; 

 •pious an!f 'rS as m Buxbawnia and Diphyscium, there is an 

 duced 'tin? P k y reduced Moss-plant, the sporogonium is not of a 

 ind murh ' 0n the contrar y, unusually large. 



<-n more probable that the Bryophytes, as a whole, illustrate a 



It seems to my 



gently sir' r r eSS1Ve Com P lexit .y- A comparison of anatomical details 

 aon strated h S< fe a P ro 2 r . ess i ve sterilisation, a process which we see 

 Version of n I , Pte "dophytes and Phanerogams, where actual 



•Vta-ive ti p * ntiall y sporogenous tissue into temporary or permanent 



Kanty though t d ^ s . occur - When it is added that the nuclear evidence, 

 ^toosoml I S i ! ls > shows the sporophyte with a double number of 

 spores the r . reducti <>n taking place on the tetrad division of 

 • c mention^ mparison w,th the segmented zygotes of algae and fungi 

 ^tfantithet- SC i ems lnevitable - The position of those who hold 



was nr^ C al J terna tion will, therefore, be that the simple sporo- 

 "T^bly som P e c u Cd as a Post-sexual growth. ~ 

 kai2 such , multicellular body as we : 



&°8enetic Si£ SUlting from ^vision of the zygote* but not necessarily 



^ ^posed a r 22 S - Uch body that we know now livin S- The land " 



restriction on fertilisation, and an alternative method of 



The starting point was 

 see nowadays in certain 



increase in numbers was an advantage. The multicellular body resulting 

 from division of the zygote provided the means for this ; the cells 

 developed separately as dry, dusty spores. As the number of divisions 

 increased the powers of the plant to nourish, protect, and disseminate the 

 spores became the measure of the number produced. Hence followed 

 the elaboration of the nourishing and disseminating mechanism, which 

 has involved a diverting of some cells from their first office of spore-pro- 

 duction, the start being, perhaps, made in a manner similar to the 

 formation of the peridium in the uredineae. To my mind— taking the 

 bryophyta alone— there is an inherent probability in all this, which far 

 counterbalances any of the obstacles which have been raised against it. 



The greatest obstacle is the fact of apospory in mosses. This departure 

 from the usual alternation will be more generally discussed in relation to 

 the ferns, where it is more frequent. Besides its being artificially induced 

 in mosses by special treatment, it appears also to have been noted by 

 Ugo Brizi in Nature, in the case of atrophied capsules of Funaria, which 

 had buried themselves in the soil. The essential point is the production 

 of the sexual generation by direct vegetative growth from the neutral. 

 This would appear to involve a reduction of chromosomes, but Pring- 

 sheim's drawings show nothing analagous to the usual process of tetrad 

 division to form the spores ; the reduction, if it occurs, must be effected 

 in some other way. 



A theoretical suggestion on this point will be made later. Meanwhile 

 let us estimate its probable importance as regards the bryophyta. It 

 cannot fail to strike the observer how uniform is the alternation in these 

 plants ; there are, I believe, no recorded cases of deviation from the 

 normal alternation in liverworts. I know of only a single case of apospory 

 among mosses taken in the open, and then in atrophied capsules ; 

 apospory, when induced, follows such extreme treatment as chopping the 

 sporogonium into pieces. And it is not as if the mosses and liverworts 

 had escaped detailed observation ; hardly any group of plants has been 

 more carefully examined by competent observers. Deviations from strict 

 alternation then are rare, and appear under physiological stress. This 

 great group, which includes the simplest sporophytes among archegoniate 

 plants, is also singularly constant in its alternation. I think this is to be 

 connected with the permanently dependent condition of the sporophyte ; 

 its equable physiological condition, nursed and protected by the moss 

 plant, finds its morphological expression in its comparative uniformity. 

 Conversely the independent position of the sporophyte in ferns, and its 

 exposure to varied conditions may have elicited more freely in them 

 unusual developments. 



( To be continued. ) 



TlGRIDIAS. 



The Tigridias or Tiger Flowers are truly remarkable members of the 

 great family of Irideae— remarkable for large and handsome blooms of the 

 most gorgeous and varied hues, some of which display white, yellow, 

 orange, and scarlet in striking contrast, whilst others are heavily spotted 

 and blotched with black and red on yellow, white, and purple grounds. 

 These spots or blotches, which thickly cover many of the flowers, have 

 procured for them the popular name of tiger-flowers. Various species 

 and hybrids of Tigridias have been introduced in recent years with the 

 natural sequence of increased interest being shown in them, and a greater 

 demand for these Mexican bulbs. Ease of culture is a distinguishing 

 feature, if a dry, sunny border can be devoted to them — as they then 

 prove quite hardy and may remain in the soil throughout the winter ; but 

 if grown in heavy or damp soil it may be advisable to lift and store in 

 sand until the severest weather is past and over. 



Although the blooms are very evanescent, being truly " flowers of a 

 day," this is fully counterbalanced by the quantity produced, if good 

 culture obtains. As above mentioned, a dry, sunny border suits them 

 best, a light, rich soil being necessary to bring them to the greatest 

 perfection, a position frequently recommended for their cultivation 



under the breakfast-room window, as, generally speaking, 

 be found on the sunny side of the house, and, further- 

 to the best 



being 

 this will 



sunny 



more, the tigridias always appear to the best advantage during 

 the early hours of the day, for many flowers, in full bloom then, 

 are decidedly passee after noontide, but only to be replaced 

 by others the following morning. For indoor culture the bulbs may be 

 potted as soon as received, in November or December, in a sandy loam, 

 to which some growers prefer to add one-fourth of peat. W ater 

 sparingly throughout, to avoid anything like stagnation. After flowering 

 is over grant perfect rest in a dry and frost-proof place. It is only fair 

 to state that much better and stronger plants are obtained from the open 

 border granted the essential conditions of success, than from pot 

 culture. The normal period of blooming is from June to August. 



The following list, though very incomplete, includes some of the 

 oldest and best known along with a few noteworthy novelties. Tigridia 

 pavonia orange-red, well known, very showy; T. p. grand iflora alba, 

 large and beautiful flowers, white spotted with crimson ; T. p. g. a. 

 immaculata, pure white, a perfect gem ; T. p. g. aurea, petals rich old 

 zold colour mottled chocolate, very fine ; T. p. conchiflora (the Shell 

 Flower) is yellow, crimson spotted ; T. cananensis, yellow, with fine 

 scarlet spots ' T. Van Houttei, yellow and chocolate brown, a charming 

 little species - T. violacea is very pretty, with violet-dotted centre, a 

 true Mexican. In addition to the foregoing we have T. Pringlei, a 

 kind of glorified T. pavonia ; and T. Patscuaro, with bell-shaped flowers, 

 white-tipped and blotched with crimson lake, a decided acquisition. 



A good border of mixed Tigridias always proves an attractive feature, 

 for in ft we may have many hundreds of curious and beautiful flowers, 

 with scarcely two alike, embracing all the colours of the rainbow, 

 crmtpsauelv mixed and blended. It also affords a daily transformation 

 scene Surely these "Mexican Day Lilies" are equalled by but few, 

 and surpassed by none, the cultivator being amply repaid for the little 

 time and care bestowed upon them. 



Rtpon. F - Dixon. 



