October 1, 1890.] 



KNOWLEDGE 



231 



injiorescmce. Inasmuch as the branches generally arise in 

 the axils of leaves the phyllotaxis is intimately connected 

 with the intloresceuce, so that the consideration of the 

 one leads naturally to the discussion of the other. 



The leaf which subtends a flower is generally much 

 simpler in structure than the ordinary leaf; it is called 

 a Imict. It is sometimes coloured,'' as for instance in 

 (Jlrnnlfmlron, a climber which grows to profusion in one 

 of the glass-houses at Kew, in which they are white, and 

 so set off the brilliant crimson flowers. The stalk of 

 the flower is termed the jiethmdc ; on it generally arise 

 one or two small leaf-like organs, called hravteolcx. 

 In Monocotyledons (ex. Hyacinth) there is one, in 

 Dicotyledons (ex. Mallow) two ; thus the number of 

 bracteoles on a peduncle is the same as that of the 

 ■cotyledons or seed-leaves with which a plant is furnished. 

 The forms of inflorescence seem endless to the tyro in 

 botanical lore, but they can all be referred to two main 

 types — the lldccmonc and i'ymosv. Of course, we do not in- 

 clude in our classification those varieties of branching to 

 which the floral axis seems subject when exhibited on wall- 

 papers. The floral axis may grow on indefinitely, pro- 

 ducing leaves in the course of its growth ; in the axils of 

 these leaves flowers or groups of flowers may arise, and 

 ultimately the axis itself may terminate in a flower. 

 When such is the case, an indi-Jinite or niri'iiiose inflor- 

 escence is the result. As the oldest leaves and flowers are 

 at the bottom of the shoot, and the 

 youngest near the apex, this form of 

 L inflorescence has also been termed the 

 ^ (rntri])Hfil or centre-seeking. The sig- 

 nificance of this last name will be 

 evident from the diagram (Fig. IV. 

 (/'), ((■), in which the observer is sup- 

 posed to be looking upon the inflor- 

 escence from above and to see the 

 lielix or spiral windmg snake-like round 

 the floral axis until it at last reaches 

 the object of its desire,, the apex of 

 ''"■■ '^- the shoot itself. Racemose inflorescences 



are very common, and perhaps the raceme itself is as 

 frequently met with as any. We may first cite the 

 Kiilitdni (ixilUtnj form, ex. AnaiiaUix (irrciixis [Yig. III. («)), 

 where a single flower arises in the axil of each leaf 

 of the ordinary stem. The Biicenw is a floral shoot 

 which generally bears leaves, and in the axils of each of 

 these leaves a single-stalked flower arises (ex. Migno- 

 nette and see Fig. III.). Being a form of indefinite 

 inflorescence, the oldest flowers are of course situated 

 at the base of the shoot. In the corymb (Fig. HI.) the 

 flower-stalks or peduncles of the raceme have elongated 

 so as to bring all the flowers to the same level, while in 

 the spike (ex. Verbena njliiimdix and see Fig. III.) the 

 peduncles have not developed, and so the flowers are 

 xcssilc. Contract the main stem of the raceme and the 

 umbel is formed (ex. Hahni licUx, the Ivy, and see Fig. 

 III.), and telescope the floral axis of the spike and the 

 result will be the capitulum (Fig. III.); ex. VhIUs jicirunix, 

 the Daisy. Slightly invaginate the capitulum of the 

 Daisy and the inflorescence seen in Dorstenia wiU appear ; 

 and continue the invagination, and you will get the 

 hollowcd-out floral axis of the /■'/'/ (Fig. III.). These 

 various forms tlnis all lead into one another. 



A Cijiitiisc, or definite inflorescence, is produced when 

 the main stem ends in a flower. The simplest case is the 

 xolitdiij tiTiiiiiKil, in which no further development takes 



place, ex. Gentianella. But generally a bract appears 

 before the flower arises, and in the axil of it a lateral stem 

 appears, which in turn ends in a flower, but before doing 

 so also produces a bract, in the axil of which stem number 

 three arises ; and so on. This is a unipiiniux form of 

 cymose branching, which generally results in the formation 

 of a false axis or m/nijiocliKui, because the upper portion of 

 each stem unites with the basal part of the succeeding 

 stem, thus giving the whole inflorescence the appearance 

 of a single racemose shoot. Its true origin can be detected 

 by the fact that the leaves are not at the base of the 

 flowers, but are situated either at the side of them or oppo- 

 site them (see Fig. V. 2 (/-), 3 (i)). If the branching take 

 place continually on one side a hAuoid cymose, a very un- 

 common form, is produced. This is so called because the 

 whole branch system appears like a helix or spiral when 

 the angular divergence of the successive branches is less 

 than one-half (see Fig. V. 3 (n) and 3 (</)), the latter of 

 which is a ground- plan of such a case. Were it only half, 

 the ground plan would represent the order of development 

 as a straight line (Fig. V. 2 (c)). The xrorpioid (ex. 

 Helianthemum, Rock Rose) is the result of the successive 



* In botanical language an organ which is not greon is said to be 

 coloured. 



branches appearing first on one side and then on the other, 

 so as that in the ground-plan we have the appearance of a 

 zig-zag or scorpion's tail (Fig. V. 3 ('/)> (f)- (''))• The 

 flowers of Stellidia, the Stichwort, order Viiri/opln/lteiv, 

 furnish splendid examples of another form of cymose in- 

 florescence—the biiHiniu.s. In these the main axis ends in 

 a flower as before ; but here, instead of producing one 

 bract before so doing, it produces two situated opposite one 

 another, and in the axils of each a flowering shoot arises. 

 These in turn branch, and so on, until there appears an 

 inflorescence like that diagramniatically represented in 

 Fig. V. (/'). in which (c) is a ground-plan. It often 

 happens that the main stem and the successive stems do 

 not elongate after the production of the pair of bracts, so 

 that when the flower which terminated each has died 

 away, each shoot appears to have divided in a bifurcated 

 or dirliiitdimiKx manner. The term " falsely dichotomous " 

 is used in describing such an one ; the Miseltoe aflbrds a 

 good example of it. 



As illustrating the two types of inflorescence only simple 

 types have been cited ; but, besides these, there are com- 

 pound forms in each division, and the two divisions are 

 linked to one another by mixed forms or those which com- 

 bine the characters of both. These are exceedingly 



