« 이전계속 »
Salter carefully describes in this Memoir. The most remarkable feature of these monstrous Passion-flowers (Passi/lora carulea and -P. palmata) consists in the circumstance that in certain malformed ovaries, which were more or less split open at their upper end, there were found, attached to the placentiferous sutures, ovular developments containing pollen-grains. The ovules low down in these ovaries were, usually, nearly or quite normal in structure. A little higher up, or intermixed with the normal ovules, were others, externally similar and anatropous, differing only in the nucleus containing a few grains of pollen. Still higher in the ovary, the ' ovules' departed further from the normal condition, and instead of being anatropous, consisted of a globular or oval extremity, supported by a more or less constricted pedicel. The thickened extremity consisted of a chamber filled with pollen, surrounded by a proper endo- and exo-theeium. Higher again, and upon the margin of the open ovary, these polleniferous, more or less ovuliform, bodies passed into antherlike organs. Figures are given of the principal modifications of the pollen iferous organs referred to.
With regard to the morphological aspect of the conditions first described, unless the case of these Passion-flowers be regarded as one in which the plant has become hopelessly ' deranged,' in defiance of the order which is usually to be traced, regulating even the insanest freaks of nature, it may serve as some little encouragement to those who regard the placenta as an axial development, in this instance bearing both ovule-buds and reduced stamina! leaves. It may perhaps be argued that the ovary of Passi/lora is not carpellary at all. Indeed, if we admit, as many now do, that the inferior ovary is in many cases an excavation of the axis, there seems no good reason why, sometimes, the superior ovary may not be a similar development prolonged beyond the outer whorls of the flower.
We do not feel that this case, so far as it has been described to us, warrants much speculation in this direction, and we are precluded from entering upon a full discussion of the morphological relations of these structures, since Mr. Salter affords us no information as to the relation of the pollen-containing sacs, found in the ovuliform bodies, to the nucleus of the modified ovule, or to its coats. All that he says is:—
"As regards the particular part of the ovule which developes the pollen, the situation in which it takes place suggests the idea that the embryo-sac may be the seal of this change when it occurs in ovules otherwise perfectly formed. 1 cannot imagine that, iu those other polleniferous organs in which the ovular anatomy has been entirely lost, or much perverted, an embryo-sac conld have had an existence, or that there had been any tendency towards its formation. It does seem probable, however, from position, where anatropous ovules have contained pollen, either that the cells of the embryo-sac, or, if they have not been as yet specialized, that that part of the nucleus about to furnish the embryo-sac, had constituted the parent cells of this misplaced pollen. The question, however, as to whether the embryo-sac had existed prior to the pollen, appears to me simply of interest in reference to the state of development which the ovule may have attained when the sexual divergence took place."
Regarded physiologically, Mr. Salter's discovery appears, at first sight, to have an important bearing upon the agitating question of parthenogenesis in plants. He says himself, "I conceive that their "paramount interest is physiological, both in the abstract in refe"rence to the question of sex, and in their consequences as to the in"fluence which such facts must have on the interpretation of cases, "or supposed cases, of parthenogenesis in phanerogamic plants."
On consideration, however, wo fail to see that the bearing of tho case is of any " real practical importance in reference to the question "of virgin-reproduction in flowering plants." Mr. Salter says:—
"The circumstance that an ovule within an ovary may contain pollen in juxtaposition with another ovule normally formed, and capable of ripening into a mature seed, appears to me to cast a grave suspicion on many of the cases of reputed parthenogenesis in phanerogamic plants. It might surely be conceded (upon the facto which I believe I have now established) that no supposed case of parthenogenesis can be considered proved unless the ovules have been subjected to microscopical examination: I am not aware if such scrutiny has been made in any of the reputed cases."
But in Coelebogyne the ovules have been most carefully examined, as the account of them given by Braun and Radlkofer sufficiently shows. Moreover, in this, the best established case of parthenogenesis, but a single ovule is contained in each coll of the ovary.
Mr. Salter says :—" The splitting of the ovary and the develop"ment of polleniferous organs in the carpels were always concurrent, "and to a great extent proportional in degree." This circumstance suggests two questions to him, viz.:—" Is the want of union of the ventral sutures the result of an antheroid development, and with the object of permitting the pollen to escape? Or, does the splitting of the ovary, by exposing the ovules, supply a physical condition which tends to convert incipient ovules into polleniferous organs?" "We cannot recall a case from any other plant which may be looked upon as evidence in favour of an affirmative answer to tho second query. In Primula, which sometimes has the placenta exposed by a monstrous condition of the upper part of the ovary, we have not observed that the ovules are affected, and among Gymnosperms, in which the ovules are normally exposed, we find no tendency to produce polleniferous ovules.
If Mr. Salter's Passion-flowers continue to produce these singular bodies, we would recommend a very careful and minute investigation into the relation of the pollen and its mother-cell to the parts of the normal ovule.
XV11.—Cebati Awd De Notabis's Asctoebous Spdleeiacei. Schema Di Cxassificazioite Degli Sfebiacei Italici Aschiqebi
PITT O MEIfO APPABTENENTI AL QENEEE Sph^bia NELL'ANTICO
Bigitificato Attbibtjitogli Da Pebsoon. Per V. Cesati o G. De Notaris. Genova, Tipografia del E. I. de' Sordo-muti, 1863.
Those mycologists who have turned their attention to the Sphreriacei, and who have watched the progress of microscopical inquiry during the last 10 or 15 years, will be well pleased at the appearance of this essay. The names of the authors are a sufficient guarantee that the subject has not been approached without due consideration, and will i-iisure for the work the respectful attention of all observers interested in the progress of cryptogamic botany. The masterly disposition of Fries in the Summa Vegetabilium Scandinavian, would naturally be the ground-work of any attempt to re-arrange the classification of the Sphariacei, and it is only from the characters disclosed by the microscope that any material aid towards such a re-arrangement can at present be expected.
The authors have done well in confining themselves to the ascigerout Sphreriacei; the time has not yet arrived for attempting to form any general views upon the apparently nearly-allied, but obscure, sporiferous genera, many of which are supposed to be only imperfect forms of ascigerous species. It may be useful, in the first place, to offer a few remarks upon the introductory part of the present work, in which the authors set forth the principles by which they have been guided in the construction of the systematic arrangement which follows, and then to notice the several genera of which that systematic arrangement is composed.
The introduction traces out the successive views of the different botanists who hare, from time to time, treated of this class of Fungi. It commences with a short abstract of Persoon's arrangement, followed by a notice of Schmidt's "Tentativo d'una classazione delle Sferie," the production of a school of botanists, of whom it is said that they wished to make nature subject to their own metaphysical theories, and aimed at the synthesis of facts, before analysis had furnished the details.
The effect, whatever it might have been, of Schmidt's lucubrations was counteracted by the contemporaneous appearance of Fries' "Synopsis Scleromycetum in Suecia nuper detectorum," which was shortly followed by the second volume of the "Systema Mycologicum," and this again by the " Summa Vegetabilium Scandinavioe."
In their short remarks upon this latter work, Messrs. Cesati and De Notaris do not seem to have correctly estimated the systematic alterations which it introduced.
They say, "Al quale metodico scompartimento (the Synopsis "Scleromycetum) tenne dietro ben tosto lo schema elaboratissimo, "che sta nel II. Volume del suo systema mycologicum (1823) e solo "signoreggid la classazione delli Sferiacei sino al giorno in cui quel "venerando Nestore della scienza, facendo gia circospetta ragione "ai resultamenti della microscopia, nella pregevole Summa Vegeta"bilium Scandinavise (1849), eseguiva in tutta la Sferiologia una "riforma abbastanza radicale, per l'epoca, facendovi valere in modo "assai esplicito t caratteri carpologici interni* delli Sferiacei." . . .
The carpological characters given in the Summa Vegetabilium Scandinaviae are certainly not the strong part of the work. These characters are only slightly alluded to, and when mentioned are not nnfrequently incorrectly described. Indeed Fries seems to have felt some misgiving that he had not attributed sufficient weight to the distinctive features of the fructification, for he says in the preface, "ignoscant, precor, hodierni mycologici, qui omnem vim in subtilia"simis notis ponunt, h»c omnibus vegetationis et morphoseos con"grua genera, ut primo obtutu mox recognoscantur, ex sporarum "et ascorum differentiis, mihi minime ignaro, impossibile fuisse "divellere."
The basis of the arrangement propounded in the present work may be stated shortly, as follows:—Considering the individual spherules (perithecia) as the fruit, the vegetative portion of the plant must be sought for elsewhere. That the stroma does not ro
* The italics arc the authors.
present this portion is sufficiently proved by the following considerations. In the first place, the stroma manifestly represents a superior grade of development in the vegetative apparatus of the plant, preparatory to the final act of fructification ; it is in fact a true receptacle, a state of inflorescence, more or less suppressed, not different from certain special processes which occur in such phamogams as Urticacea;. In the second place, that which is called the stroma does not always belong to the fungus. The swollen, or placental body, which bears the perithecia, may be entirely formed from the matrix, which, by contact with the primitive stroma, or with the true vegetative apparatus, is, by physiological action, transformed into a receptacle; apparently belonging to the Sphaeria.
Even when the stroma is autonomous it does not always precede the perithecia, as there are strong grounds for suspecting, even if it cannot be said to be proved, that, sometimes by the effect of transudation, sometimes by a centrifugal expansion of the external stratum of the perithecia, a sort of posthumous stroma is formed; so that there are reasons for believing that the perithecia cannot always be considered as organs of fructification pure and simple, and that, in those cases where the external stratum of the perithecium is suberose, woody, or carbonaceous, such stratum must be looked upon as a continuation of the stroma, as a receptacle of a peculiar kind, analogous to the thalloid excipulum of the lichens.
The authors express their ultimate opinion, with regard to the value of the stroma as a characteristic, by saying, that the gradations from one to another of the different known forms, are such as to prevent any precise classification founded upon the features of the stroma; that, in the larger groups and genera, the latter should only be taken into account when its nature is well-defined, and when it is clearly distinct from the mycelium and from the matrix, in which case it becomes a character of primary importance.
The nature and value of the stroma being thus disposed of, the authors proceed to state their opinion, that the substance and texture of the perithecia, and the form and nature of the sporidia, are the points of most importance in the classification of the Sphawiacei. Most mycologists will be disposed to agree generally in this view, although there might be a difference of opinion as to whether the characters derived from the perithecia, or those derived from the sporidia, are .the most valuable. It is obvious, however, that no arrangement would now be practicable which did not combine the two: it would
N. H. R.—1864. G