September 1, 1894.] 



KNOWLEDGE. 



211 



or lower member of the outer staminal whorl of the lily ; j 

 four of the others are frequently represented by protuber- [ 

 ances or staminodes, while one is, as a rule, completely 

 aborted. The lady's-slipper orchid, Cypripedium, has a 

 large staminode representing the fertile stamen of orchis ; 

 its two perfect stamens correspond to the two anterior 

 ones in the inner whorl of the lily. All three stamens of 

 the outer whorl are present at first in the bud of Calanthe, 

 but only the anterior one is ultimately developed. Urope- 

 (iium lacks the outer whorl, but has the inner one complete, 

 all the three stamens being perfectly developed, while five 

 often, and occasionally the whole six members of the 

 andrcEcium are present in Isochilus. 



The andrcecium of Iridacese consists of three stamens 

 homologous with the outer whorl of the lily ; the inner 

 whorl is entirely suppressed. Although the irises are in 

 some respects intermediate between Orchidacefe and 

 Liliaces, the fact that among the orchids sometimes the 

 inner and sometimes the outer staminal whorl is represented 

 shows that they cannot be directly derived from the iris 

 type. There is apparently only one possible interpretation 

 of such facts ; they point distinctly to the six-stamened IDy 

 as the type from which both orchids and irises have 

 diverged. This interpretation is strongly supported by 

 anatomical considerations, the number of vascular bundles 

 or leaf-traces present in the flower-stalk being such as we 

 should expect in accordance with this view. These homo- 

 logies, which are exhibited in the foregoing diagrams, afford 

 as strong evidence as perhaps can be given of the origin of 

 different species, genera and orders of plants by descent 

 and modification from a common ancestral form. 



Notwithstanding their odd and irregular shapes then, 

 all orchids may be referred to the simple lily type. The 

 single fertile stamen of orchis bears the same relation to 

 the six stamens of the lily that the single enlarged toe of the 

 horse does to the five toes of the archetype from which the 

 horse is supposed to be descended. Cypripedmm, Calanthe 

 and to some extent the irises stand very much in the 

 position of the eohippus and miohippus, since they 

 represent intermediate phases in the development. In 

 the floral series the theoretical line of descent is indicated 

 by abortive stamens or staminodes, in the equine series by 

 rudimentary and functionless digits. 



Like the perianth of the lily, that of the orchid is 

 composed of a sepaline and petaline whorl, each containing 

 three leaves or segments, but while the parts of each whorl 

 are alike in the lily, in the orchid they are dissimilar. 

 This irregularity of the perianth arises mainly from the 

 enlargement of the lip or labellum, which is usually 

 prolonged into a hollow pouch or spur ; it is composed of 

 the anterior petal combined with two of the sterilized 

 stamens. Other peculiarities of the orchid which may be 

 mentioned in passing are the gynandrous condition caused 

 by the adhesion of the fertile stamen to the style, the 

 modification of one of the three typical stigmas to furnish 

 sticky discs for the pollen masses, and the twisting of the 

 ovary by which the labellum, which is uppermost in the 

 bud, is brought down to the lower or anterior side of the 

 flower. 



The degraded and aberrant blossoms of grasses are 

 connected with the lUy type by a corresponding series of 

 transitional forms. Bamhusa, which has six stamens, 

 differs from the type only in the absence of the outer 

 perianth-whorl, but in most grasses the posterior leaf of 

 the inner perianth-whorl has also disappeared, together 

 with the whole inner whorl of stamens and the anterior 

 carpel ; the latter is the only member of the carpellary 

 whorl present in the mat-grass, Xardux. The flowers of 

 sedges are also fashioned on the Uly pattern, the three 



inner stamens being suppressed as in iris. Zingiberese 

 agree with orchis in ha%-ing only one fertile stamen, but 

 its position in the ginger order is posterior, not anterior 

 as in the orchid ; the rest of the six-merous androecium is 

 represented by petaloid pieces. The allied Canna or Indian 

 shot has Hkewise all the members of the androecium 

 developed as petals, with the exception of one which bears 

 pollen, and is half petal, half stamen, as indicated in the 

 diagram. 



Facts of this description, and many others which might 

 be mentioned, go to show that such regular six-merous 

 flowers as we find in Liliacese, Amaryllidacefe, Juncacefe, 

 and Palmacere, represent the primitive type from which 

 most, if not all, existing monocotyledons have been derived. 

 Although other divergences of character have occurred 

 independently, which make it impossible to trace the 

 actual descent or phylogeny of a particular species, still 

 there is little difficulty in following the steps by which any 

 single character has been acquired. 



Equally striking are the relationships rendered apparent 

 by the floral diagrams of dicotyledons. In the vegetable, 

 as in the animal kingdom, the excessive repetition of 

 similar parts is held to indicate a low gi-ade of organization. 

 The simplest flowers in the dicotyledonous class consist of 

 many parts ; the Nymphace® and Cactacese have numerous 

 sepals, petals, and stamens, arranged in a spiral or acyclic 

 manner. A corolla, consisting of twelve petals, occurs in 

 the house-leek Sempervkum. The numerous stamens of 

 the rose, buttercup, and poppy constitute a feature which 

 these flowers have doubtless inherited from very remote 

 and simply organized ancestors. The first two also possess 

 numerous distinct carpels, another mark of primitive 

 simplicity. 



The great majority of dicotyledonous orders, however, 

 admit of being referred to a floral type, consisting of six 

 alternating whorls containing five parts each, viz., a 

 sepaline, a petaline, two staminal, and two carpellary 

 whorls. A close approximation to this type occurs in some 

 of the crassulas or stonecrops. The geraniums have 

 the formula S.5, P5, StlO, C5, which diflers from the 

 type only in the absence of the inner whorl of carpels. 

 This whorl is rarely developed, possibly for want of room 

 on the apex of the floral axis. If the number of parts in 

 the diflerent whorls correspond the flower is sj-mmetrical, 

 but the carpellary whorl is so often incomplete that it is not 

 taken into account in reckonmg symmetry. The number 

 of carpels varies greatly even within the limits of the same 

 order; thus among the Caryophyllacese it fluctuates from two 

 to five. The presence of two carpels, on the other hand, is 

 a constant character of the order Scrophulariacese, whUe 

 the Leguminosae never have more than one. The evident 

 tendency to reduction observed in the carpellary whorls 

 shows that there is a struggle for space among the floral 

 organs leading to the elimination of superfluous members. 

 Not improbably the difficulty of accommodating many 

 members on the floral axis may originally have led to the 

 establishment of the six whorled type as an improvement 

 upon an earlier model made up of an indefinite number of 

 perianth-segments, stamens and carpels. A good example 

 of the struggle for existence among the organs of the same 

 flower is seen in the calyx of the rock rose, Heluintkeinum ; 

 three of its sepals are much enlarged, but this has 

 apparently taken place at the expense of the other two, 

 which are quite rudimentary. A symmetrical decrease 

 affecting all the whorls in the same manner is met with in 

 the yellow tormentQ ; the potentillas generally have five- 

 merous flowers, but in P. tormentilla the calyx and corolla 

 have only foiu- parts each. The same thing occurs in 

 Eubiacese, Eubia having five-merous, Galium four-merous 



