On the Development of the Andrcium in Cochliostema, Lem

204 DR. N. T. MASTERS ON THE DETELOPMEXT OF On tlic Development of the dndrecium in CochZiostenzn, Lem. By M. T. ~IASTERS,KD., P.R.S., F.L.S., &c. [Rend March 7, 1S’iS.I [PL LTE m.] INthe ‘ Gardeners’ Chronicle’ for 1S63, pp. 264, 323, I had occa- sion to describe that most remarkable and beautiful plant Coch- liostenm Jucobiniiuitt, Lcm., and to give the history of its intro- duction into this country. At that time I was only enabled to exailline adult flowers, and, with seine imprudencc it must be con- fcssed, I hazarded a theory as to the peculiarities of the stamiiinl apparatus. I have since studied the course of devclopment of the flower in question ; and, as a result, I find that while my iiescrip- tioii of the adult flowr JJXS in the main accurate, my theoretical es- planation of its peculiarities rras in niany respects erroneous. It is vith the TieJT of correcting these errors and induciug others to incestigate the peculiady reinarkable structure of this splendid plant, that I norr beg to lay before the SocietF the follon-ing par- ticulars as to the development of the flon er, and especially of the andrcecium. The floirer first appears in the form of a globular tubercle (Pl. IT. fig. I), on one side of wliich shortly appears a thick semiluuar prominence, which is the origin of the posterior sepal (fig. 2). The two remaining sepals are formedin succession, one after thc other(fig. 3). I have Iierer absolutely secn the flower with two sepals only ; but, from the small relatire size of one of the thee sepals (that placed nest the bract) and from analogy Kith other florrers, I haye no doubt that the three sepals are formed in succession. If the three sepals be turned back rrith the dissecting-n’eedle, as shorrn in fig. 4, the central gron-ing point inay be seen to haTe lost its glo- bulatj foriii, to haye assuiiied a triangular outline, and to be some- what depressed at the top. From the three corners of the central growing point protrude simultaneously the thee petals (fig. a), which only precede the appearance of the starnew by a very short interval-so Simt, indeed, that one inay esainine a great many flovers before fincling one in which the petals alone arc formed nithout indications of the stamens. At this period the superiority in relatire size of the posterior and first-formed sepal is Tery mnrl~ccl. AS to the andrcfciuin, it is perfectly cleni. that this consists of six eleinents ; oud all analogy would suggest that thesix portions THE AXDZECICX IX COCHLIOSTEXA. 20.5 should be in txo i*ows, one within the other, the innermost developed bubsequently to the outer. I cannot assert positiTely that this is not so ; all that I can say is, that after examining several floners I liare never been able to see that the andrcecium follows this caurse. It has always appeared to iiie that the three posterior stamens are clm eloped at about the same period aid in advance Of the three anterior ones (figs. 6,S, 9) ; at myrate, shortly after the petal, have nianifestcd themdws, the anihceciuni niay be seen to consist of three tubercles at the back of the flower, all three of about equal size, and of thee anterior tubercles much sqaller than the posterior ones, and of uuequal size, the central one being much smaller than the other trio (figs. 8, 9). The position of the staminal tubercles is as follow: the odd posterior stamen is opposite the first-formed sepal j the two postero-lateral stamina1 tubercles are opposed to two corresponding petals. Of the three tubercles in the anterior part of the flower, the tiyo lateral are opposite the sepals, the central one is opposite the anterior petal. The arrmgement, then, of the stamens is quite consistent with their disposition in ti\ o ron s formed one after the olher, though, as before stated, I hare not been able to satisfy myself that, in point of time, there is any such regularity of appearance. Fol- loxing the coiirx of the andrecium from this point, it will. be seen that the superior size of the thee posterior staminal tubercles is maintained, that they become notched at the summit (figs. 10, ll),and speedilF present traces of anthers. The three anterior tubercles, on the other hand, progress very slowly, and never form authers at their summits (fig. 12). It is now evident that the two antero-lateral tubercles are tho lateral " staminodes '' of the adult flower. The central tubercle is the least developed of the thee ; in fact it often ceases to grow, so that in the adult floner it fre- quentlphappens that it is oyerlookcd, or that it is really absent. Up to thi, time the six stamina1 tubercles hue been dibtinct ; but now, by the further growth of the entire andrcecium at the base, a shal- lon- tube is formed, the margin of n-hich bears the stamens and staininodes as just described. On ing to the relatively increased gronth on the posterior side of the flomi- as compared with that on the anterior half, the staminal tube is much deeper on the foorincr (fig. 13) than on the latter side (fig. 12); and it retaius this inequality to n wry marked degree in the adult flower, vhere? indeed, the three posterior stamecs niay be seen alxays inseparate for nearly half their length, Thile the two antero-lateral stami- Q2 206 DR. 31. T. MISTERS OX THE DETELOP3TEJT OF nodes are quite detached. The anther, in the early stages of its existence, is an ordinary tn-o-lobed structure (fig. 12), eacli lobe beiiigagniu subdivided into two minor lobules bj-a slight depression. There is at first no trace of the spiral curvature which afterwards becoinzs so remarkable a feature of these plants. The connective in the odd posterior stamen remains horizontal, Khilst in the t1.i.o postero-lateral anthers it assumes gradually a rertical position. The direction of groTtli of the anther, as of the coil, is centrifugal, i. e. froni the centre outwards and up\~ards(fig. 14). Not till after the anthers begin to inaiiifest the spiral coil is there ally indication of those petal-like hoods \\ hich couceal the anthers in th adult flower, of which they constitute so remarkable n feature. The course of development slioivs them to be inere petaloid out- growths from the sides of each of the postero-lateral filnments, grad~iallyincreasing till they coillpletely euvelope the authers (fig. 13). During this yrocess the anther of the posterior centrd stamen, which heretofore had maintained its proper position, be- comes, as it irere, pressed to the front in advance of the tw-o lateral anthers, and thus in the adult flower may give rise to the false impression that it is really aid organically interior (figs. 16, 17), an impression I myself had denI first described the structure of the flower. Not till the stanleiis have assumed the cha- racters and positions just mentioned is there any indication what- ever of that curiously lobed and ciliated process which I formerly regarded as a staminode belonging to an outer series of abortive stamens. It is, despite its pojitioii and prominence in the adult flower, a mere outgronth from the thalamus. at the back of the flower (fig. 18). TT'hat, if any: iuorphological significance, or what physiological office it may have, is at present uuknon-n. It may be connected in some "ray \\ ith the process of fertilization j but this is a mere guess. The de~elopmentof the pistil presents nothiilg notcn ortliF or dif- ferent from what occurs in many otlier Endogenous flowers. Its three conponeut carpels are formed simultaneously-one posterior, two autero-lateral. They make their appearance soon r.fter the for- mation of the staiiiinal tubercles, aiid before an!- iudicntion of anthers is prescut (fig.8). The carpels are closed, adthe stjle formed, before the occurrence of thoce remarkable changes in the stamens dread>-:illucd to. It is only after repeated exmiinations that I venture to lay before the Society the results of my observtions on the dwe- TIIC .4RDB(ECKJJI IS COCHLICSTE3L.L. 207 loplnent of this remarkable flowr. I liave the inore hesitatioii iii cl.oiug so, as the course of development iii the andrceciuin is so differcut from that described by Payer in Tradescniztia or Coii!- me?yizn*. For the sake of comparison I add a bricf abstract of the conclusions arrived at by the eminent French snvnnt. Payer dcscribes the sepals as deyeloped in succession, the latest being the anterior one or that superposed to the '' h-nctie mdre ;" the petals are described as simultaneous in their appearance-one placed internally, one esternally, aucl one, half iilternallg, half externally. So far niy observations are quite in accordance with those of Payer ; but in the case of the aitdroecium there are ma- terial discrepancies, as dlbe obvious from a coinparison of what has been previously stated with Payer's account of the development of the stamens iu the regular-flowered Trndescanfia. The andrcecium, according to this botanist, consists of six stamens in two rows : the stamens of each whorl appear all at the same time ; but the meinbers of the iiiiier series, those superposed to the petale, appear first, before those placed in front of the sepals, rl wholly esceptioiial occurrence. It is unnecessary to say more as to the development of the other parts of the flon.er, or as to the inflor- escence, as ins obserdions on these points coincide with those of PaFer.

Load more