xviii OUTLINES OF . 



132. Placentas are ■ • . x ' i.i- i. • • i„r.;i/> 



axile. when the ovules are attachea to the axis or centre, that is, m pluriJo- 



ciilar ovaries, when they are attached to the inner angle of each cell ; m unilocular 

 simple ovaries, which have almost always an excentrical style or stigma, when the 

 ovules are attached to the side of the ovary nearest to the style ; in unilociilar com- 

 pound ovaries, when the ovules are attached to a central protuberance, column or 

 axis rising up from the base of the cavity. If this column does not reach the top 

 of the cavity, the placenta is said to be free and central. 



parietal, when the ovules are attached to the inner surface of the cavity ol a 

 one celled compound ovary. Parietal placentas are usually slightly thickened or 

 raised lines, sometimes broad surfaces nearly covering the inner surtace ot tne 

 cavity, sometimes projecting far into the cavity, and constituting partial dissepi- 

 ments, or even meeting in the centre, but without cohering there. In the latter 

 case the distinction between the one-ceUed and the several-celled ovary sometimes 



almost disappears. . " . , r j. i 



133 Each Ovule (121), when fully formed, usually consists of a central mass or 

 nucleus enclosed in two bag-like coat<!, the outer one called primine, the inner one 

 secuncUne. The ckalaza is the point of the ovule at which the base of the nucleus 

 is confluent with the coats. The foramen is a minute aperture m the coats over tlie 

 apex of the nucleus. 



134. Ovules are . r i.\. 



wthotropous or straight, when the chalaza coincides with the base (3fi) of the 



ovule, and the foramen is at the opposite extremity, the axis of the ovule being 



campylotropoiis or incurved, when the chalaza still coinciding with the base of 

 the ovxde, the axis of the ovule is curved, bringing the foramen down more or less 



towards that base. j j.i 



anatropous or inverted, when the chalaza is at the apex of the ovule, and tne 

 foramen next to its base, the axis remaining straidit. In this, one of the most fre- 

 quent forms of the ovule, the chalaza is connected with the base by a cord, called 

 rltax^he, adhering to one side of the ovule, and becoming more or less incorporated 



with its coats, as the oxvXq enlarges into a seed. , -, i ^^ 



amphitropous or half- inverted y when the ovule being as it were attached laterally, 

 the chalaza and foramen at opposite ends of its straight or curved axis are about 

 equally distant from the base or point of attachment. 



§ 12. The Eecqytade and Relative Attachment of the Floral Whorls. 



135. The Receptacle or torus is the extremity of the peduncle (above the calyx), 

 upon which the corolla, stamens, and ovary are inserted. It is sometimes little 

 more than a mere point or minute hemisphere, but it is often also more or less 

 elongated, thickened, or otherwise enlarged. It must not be confounded with the 



receptacle of inflorescence (74). n . , r 



136. A Dhh, or dl&c, is a circular enlargement of the receptacle, usually in the torm 

 of a cup (c)ipid(tr), of a flat disk or quoit, or of a cushion {pulvinate). It is either 

 immediately at the base of the ovary -within the stamens, or between the petals and 

 stamens, or bears the petals or stamens or both on its margin, or is quite at the ex- 

 tremity of the receptacle, with the ovaries arranged in a ring round it or under it. 



137. The disk maybe entire^ or toothed, or lobed, or divided into a number of 

 parts, usually equal to, or twice that of the stamens or carpels. When the parts 

 uf the disk are quite separate and short, they are often colled (/lands. 



13f?. Nectaries are either the disk, or Small deformed petals, or abortive stamens, 

 or appendages at the base of petals, or stamens, or any small bodies within the 

 flower which do not look like petals, stamens, or ovaries. They were formerly 

 supposed to supply bees with their honey, aud the term is frequently to be met 

 with iu the older Floras, but is now deservedly going out of use. 



139. When the disk bears the petals and stamens, it is frequently adherent to, 

 «ni1 annarpnfly forms part of, the tube of the calyx, or it is adherent to, and appa- 



mxrh nf the ovarv. or of both calvx-tube and ovarv. Hence the three 



forms part of, the ovary, or of both calyx-tube an 

 no- importaut distinctions in the relative insertion 



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