ORCHID 



1163 



is continued by an axillary bud originating in the axil of 

 one of the leaves. The whole plant is thus built up 

 of branches sympodially united. The lower part of 

 each new axis is prostrate at first and bears only scales. 



known as the rhi 

 upward and bears ordinary . 

 portion of thi- stnii l.i-t'oiii 

 reservoir known ,i - a |. . 

 itself may cchi- ' 



Cattleya. It i^ i 

 young, and b< ai - i m -. u - 

 other cases only ;l .slll.^K Uii 

 bears 1 



Later the apex turns 

 !aves. In many the erect 

 s thickened into a food 

 luliulb. The pseudobulb 

 ! internodes, as in Laelia, 

 iih leaves, at least when 

 ■ 'I' the fallen leaves. In 

 mode is thickened. This 

 lit, but has no leaf-scars. 



The new shoot which continues the growth of the plant 

 arises in the axil of one of the scales below the pseudo- 

 bulb. The manner of growth is shown in Figs. 1506 and 

 1567, in which the parts marked a a and 6 6, respectively, 

 represent the growth of a branch with its basal portion 

 or rhizome and the terminal portion or pseudobulb. In 

 the terrestrial Orchids pscudobulhs are usually not 

 formed and the erect ii.iiiion is :i I.m^' or short stem 

 clothed with leaves (S..l.iMli:i, S. 1. nii. .liiim). The in- 

 florescence is aither axilimv i 1 1. n.lr iiiiiim. Fig. 1566) 

 or terminal (Cattleya, Fi^'. ::.imI. 



The habit of the plants dipeu.Ls iu a great measure 

 upon the rhizome. When this is long the plants are 

 loose and straggling, and wlien it is short they are com- 

 pact in habit. In some the rhizome becomes suberect or 

 climbing (species of Lycaste). 



the 



2 of these 

 , etc. ) the 

 ito a wing- 

 ii..il:ir sta- 



' nit hers. 



1567. Cattleya. 

 The light and shaded parts, a a and b h, each represent 



The Orchid flower exhibits |..ii,:,|,- iIm -r,-ate 

 specialization and adaptation 1 i 

 vegetable kingdom. The 2 outer w I - 

 the sepals and petals, have been -m'l h n'l 



In the monocotyledons there an;- normal 

 whorls of stamens. In the Orchids only 1 

 are fertile. In the Monandrse (Cypripediu 

 odd stamen of the outer whorl is di-Tcloped 

 like staminodium (Figs. 1568, l."6|i. ./ 1 Th. 

 mens of theinner whorl are fertil. i I i i 

 1 on each side of the starainodiiiiii ; i ■-, \:.>\'.\,a). 



In all the other Orchids, except i I -.only 



the odd stamen of the outer whrnl i- i. ml. , ln.iringan 

 anther situated at the top of the column (Fig. 1570, a). 

 The similar two of the inner whorl are developed as 

 staminodia, forming the sides of the clinandrum or 

 anther-bed. Often they are developed into crests or ears 

 on the column. Traces of the oth. i -i:iiiii n- nr rarely 

 found in the flower. Compare I'i:; . i l- '11. \'. I. 1. 



The :! pistils are developed in i i i i ,: i .i a few 

 related genera. In these the sli-ii.i i . ;. .i 1 1 , :;.|<jhed, 

 showing the union of .I pistils |l'i;;.s. l..G^. l..i.;i. .v). In 

 most of the other genera only '1 of the stigmas are 

 receptive, the third being developed into the curious 

 rostellum. In some cases the stignuitic surfaces are 

 confluent into one, while in others they remain more or 

 li"*s distinct. Generally they appear as flat surfaces 

 often sunken in a depression in the column (Lipliinew, 

 Pig. 1570, s, and many others). In a few cases the 

 stigmas are more or less elevated on stalks (Hahena- 

 rii). In Sophronitis they extend partially along two 

 wing-like projections of the column. 



The odd pistil, the rostellum. is situated above the 



stigmas, separating them from the anther-bed. In the 

 Lfeliinese its lower surface is still continuous with the 

 stigmatic surface (Pigs. 1570, A, B, r). The principal 

 function of the rostellum is the secretion of a viscid 

 fluid, by means of which 

 the pollen masses adhere t( 



1569. 

 Selenipedium caudatum. 



f, staminodium: a, anther; 

 s, stigma. s, 3-lobed stigma. 



The anther lies above the rostellum, within a depres- 

 sion or anther-bed (Fig. 1570, a). Its cells vary from 

 2-4 or 8. In nearly all the Orchids the pollen coheres 

 in masses or poUinia (Fig. 1570, p), the number of 

 pollen masses corresponding to the number of anther 

 cells. Often the viscid substance uniting the pollen 

 grains is prolonged into a stalk (caudicle), which ex- 

 tends beyond the anther and comes itito contai-t with 

 the viscid substance secreted by the nistilluin. wliich 

 forms an adhesive disk by means of whii ti tlic ]Mi|liiija 

 become attached to insects. In many i h.hi.N iIm outer 

 layer of the rostellum itself separnt.- I,y a .lis-olution 

 of the underlying cells, and thus fonns ;l stalk (.stipe), 

 which becomes attached to tin. in.lliiiii l.\ im-ans of the 

 product of the dissolved la 11- What. \.r its origin, 

 the stalk, with its viscid di-l , r^im "H'' id' the most 

 important parts of the m..!, mi in Ix m. aiis of which 

 pollen is trans]ioiaril ti-.m il.. ii lo tlowii-. insuring 

 cross-pollination .a lla . I, tail- of tlie 



mechanism bv wiia. . a: ['h-Ia -I lia\.' laa-ll 



11' I "I the parts of the flower to one another 



is, la II an. Ill- .hanged by the peculiar growth of the 

 lUiial a.vi.s. I'liis is convex in the very young stages of 

 development, but it soon becomes cup-like and finally 

 tubular, inclosing the ovary. Special lateral outgrowths 



A. B. Section through the col- 



Column of Cattleya. umn of Cattleya. 



(7. rtiithcr : r. rostellum: ;'. poUinium: r. rostellum: 



g, stiguia .s. stigma 



1570. Details of the column of Cattleya. 



near the top of the ovary form the "foot" of the column 

 found in many orchids (Pescatoria, Phaius). When the 

 foot is present the labellum is attached to its apex, and 

 often the sepals are decurrent upon it, forming a men- 



