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dense fulvo-glandulosis: foliis angustis, sublanceolatis, acuminatis: petalis

bifidis, sepalis subduplo longioribus, conspicuis: capsulis ovatis, calyce

sublongioribus.

a fulva; dense fulvo-tomentosa.

B. submuda; glabriuscula; foliis inferioribus glabris.
Hab. rarior sparsimoue in rupibus siccis excelsioribus Maderae.
Habitus quodammodo Stellariae. Pedicelli semper erecti. Capsulae

fructiferae calyce tectae, abbreviatae, obovatae vel ovales.

58. Arenaria serpyllifolia L.
y, depauperata; viscida, glanduloso-pubescens.

Hab. in Portu Sancto: etiam in cacuminibus summis Maderae.

59. Silene filiformis, nob. S. annua, pubescens: caule erecto: ramis divaricatis, filiformibus, gracilibus, strictis; internodiis saepe viscidis; foliis angusto-lanceolatis, acutis; infimis obtusiusculis; summis raris linearibus: floribus solitariis, inconspicuis pedunculatis; pedunculis glabriusculis; calycibus oblongis; petalis linearibus, capsulisque cylindricis, sepala subaequantibus: anthophoro capsulae dimidium vix aequante. S. inaperta, Hort. Reid. quoad saltem stirpem Maderensem: haud Linn. Hab. in sterilibus apricis, alveisque siccis convallium Maderae. Flores inaperti: petala viridi-fusca. S. inapertae L. proxima; sat vero distincta.

60. Silene ignobilis, nob. S. annua, glabriuscula, dichotome ramosa, erecta: foliis inferioribus subciliolatis, spathulatis, superioribus lanceolatis: floribus solitariis, inconspicuis, pedunculatis; calycibus oblongis, haud inflatis, mox ventricosiusculis basique coarctatis, reticulatis; petalis inconspicuis, calycem vix superantibus: capsulis ventricosis, doliiformibus, calycem aequantibus; anthophoro brevissimo. Hab. inter segetes Maderae rariss. Viridis, vix glaucescens. Variat plus minus velutino-pubescens;

plerumque fere glabra. Petala apice purpurascentia.
4. A 2 -

61. Silene inflata, Sm., D.C., &c.

War. intricata nob.; vix glaucescens; caulibus ramosissimis, dense intricatis, elongatis, pendulis, basi suffrutescentibus. Hab. in rupibus excelsis declivibus Convallium Maderae.

FRANKENIACEAE.

62. Frankemia cespitosa, nob.

F. caulibus fruticulosis, ramosissimis, densissime cespitosis, humilibus, humifusis, calycibusque basi velutino-pubescentibus: foliis sessilibus, basi connatis, linearibus, glabris, margine revolutis, basi breviter et parce ciliolatis: floribus in capitulos terminales congestis, subcymosis, foliis multo longioribus.

Hab. in collibus maritimis sterilibus aridisque Promontorii Ponta S. Lourenço Maderae; etium Portàs S*.

F. ericifoliae C. Sm., necnon F. corymbosa. Desf, nimis forsan affinis.

VIOLARIEAE.

63. Viola paradora, nob.

V. suffruticosa, e basi ramosa; ramis subproductis, elongatis, simpliciusculis; inferne nudis, stipulisque simplicibus linearibus integris minutis saepe obsoletis, petiolisque elongatis marginatis ternato-fasciculatis, foliisque rotundato-spathulatis crematis basi abruptis cordatisve, glaberrimis: foliis summis cuneato-elongatis, in petiolum attenuatis, apice subtridentatis, petiolisque caulibusque subpuberulis: sepalis oblongis integris, bracteisque pedicelloque pubescentibus: calcare obtuso, calyce longiore; nectario......... capsula obsolete hexagona, glabra; seminibus pallide flavescentibus, paucis (15–20), ovatis.

Hab. rariss. in summis cacuminibus montium excelsiorum Maderae, in fissuris rupium. Invenit cl. Car Lemann, M. D.

Obs. Cum V. calcarata L. conferenda. Flos aureo-flavus. Stylus ab apice ad basin attenuatus. Stigma urceolatum, utrinque fasciculatopilosum, ore magno, expanso dilatato, inferne in labellum producto. Folia ad apices ramorum sterilium conferta. Pedunculi solitarii, axillares, subpollicares. Capsulae abbreviatae, obtusae. Semina, praeter colorem, fere ut in V. tricolore L.

CRUCIFERAE. 64. Sinapidendron salicifolium, Prim. p. 37. No. 65. Syn. Sinapis angustifolia, D. C. Prodr. 1. 220. Hab. in rupe quadam excelsa maritima, “Cabo Giram” dicta, prope

vicum Camera de lobos Maderae, nuperrime ab amico Rev". M. Tucker, botanophilo vel oculatissimo, detecta. Species genuina videtur.

65. Matthiola maderensis, nob. M. biennis: caule herbaceo, erecto, elato, ramoso: foliis oblongis, integerrimis, incano-tomentosis; radicalibus densissime rosaceo-confertis: siliquis compressis, glanduloso-muricatis. Hab. in rupibus maritimis Maderae et Portus S". ubique vulg. Flores pallide violacei, vespere praesertim odori, rarissime albi. Species intermedia, habitu foliisque M. incanae R. Br.; siliquis, 3–5 poll.

longis, M. sinuatae, ejusd. MADERA, October 1837.

SUPPLEMENTUM.

CHARACEAE.

66. Chara atrovirens, nob. C. atroviridis, pellucida, lucida, gracilis, foetens: caule ramisque tenacibus, tenuibus, flexilibus, hinc inde articulatis superne sparsim mimutissime retrorsum papilloso-spinellosis, contorto-striatis: ramulis verticillatis, 5–6-articulatis; articulis inferioribus striatis; summis simplicibus, bracteisque 2–4 inarticulatis, cylindrico-setaceis, nucula triplo quadruplove longioribus, laevibus, haud striatis, glabris. Hab. in rivulis aquarum fluentium Madera rariss. C. vulgari Ag. proxima. Differt colore, scabritieque ramorum, radicellos nascentes deflexos, sparsos aemulante.

MADERA, May 1838.

XXVIII. On a New Correction in the Construction of the Double Achromatic Object-glass. By Richard PoTTER, Esq. B.A. Queens' College.

[Read April 30, 1838.]

THE achromatism of the compound object-glass of telescopes has never, that I am aware of, been investigated otherwise than for very small pencils.

Sir John Herschel, in his elaborate and excellent paper on the aberrations of compound lenses and object-glasses, published in the Transactions of the Royal Society for 1821, when noticing the investigations of Clairaut, Euler, and D'Alembert, makes no mention of any higher approximation having been attempted; and he himself follows no other method for the chromatic dispersion, although he has pursued the subject of the spherical aberration so far as to render the objectglass free from it, for astronomical and terrestrial objects at the same time. Indeed, from the following passage in the same paper, it is clear that he did not suspect the existence of any unconsidered residual dispersion, of the magnitude of that which I am about to discuss; for he says, “The simplest considerations, indeed, suffice for the correction of that part of the aberration which arises from the different refrangibility of the differently coloured rays; and accordingly this part of the mathematical theory of refracting telescopes was soon brought to perfection, and has received no important accession since the original invention of the achromatic object-glass."

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