3 8o 



FOURTH GROUP. SEED-PLANTS. 



downwards till they reach the cavity of the ovary. The outer form of the style 

 is usually elongated-cylindrical, or filiform, or columnar, or sometimes prismatic 

 or flat and riband-like ; it is of considerable size in most of the Irideae ; very 

 long and tripartite and with each division hollowed out into a deep cup in Crocus ; 

 the genus Iris has three free broad petaloid coloured styles. Sometimes the 



portion of the style belonging to each carpel is branched, 

 as for instance in the Euphorbiaceae, where the tripartite 

 style corresponding to the three carpels is divided above 

 into six branches. The style often remains quite short, 

 and it then appears like a mere constriction between the 

 ovary and the stigma, as in Vitis and other genera. 



The stigma, in the narrower use of the term, is the 

 part of the style destined for the reception of the pollen ; 

 it is covered at the time of pollination with a viscid 

 secretion and usually with delicate hairs or short papillae, 

 and is a glandular structure which sometimes appears to 

 be merely a peculiarly developed portion of the surface of 

 the style, sometimes as a special organ surmounting the 

 style; its form is very variable and is always closely 

 connected with the way in which the pollen is conveyed 

 to it, whether by insects or by other means, and can 

 only be rightly understood by reference to these circum- 

 stances. We will only say here that the open canal of the 

 style, when there is one, has its exit in the surface of the 

 stigma; if the canal is closed or entirely wanting, the 

 stigma then appears as a superficial glandular formation 



on the apex or beneath the apex of the style or of its divisions ; if these are long and 

 slender and covered with long hairs, the stigmas are penicillate or feathery, as in the 

 Gramineae; in the Solanaceae and Cruciferae the moist stigmatic surface covers a knob- 

 like notched thickening at the extremity of the style, in Papaver it forms a many- 

 rayed star on the lobed style. Sometimes the stigmatic portion of the style is greatly 

 enlarged, as in the Asclepiadeae, where the two monomerous ovaries which are 

 elsewhere separate cohere by these stigmatic heads; the true stigmatic surface, into 

 which the pollen-tubes penetrate, lies concealed in this case on the under side 'of the 

 stigma *. 



Nectaries. Wherever pollination is effected by insects, glandular organs are found 

 in the flowers, and these organs either secrete or contain in their delicate tissue juices 

 with a strong smell and taste (usually sweet), which can easily be obtained from them 

 by suction. These juices are all included under the term nectar, and the organs 

 which produce them are called nectaries. The distribution, form and morphological 

 significance of nectaries are very various, and are always in direct relation to the 

 specific contrivances in the flower for its pollination by insects. The nectaries are in 

 some cases merely gland-like groups of cells on the leaves or on the axial parts of the 



FIG. 312. Longitudinal section 

 through the gynaeceum of Viola 

 tricolor ; SK ovules, gk canal of the 

 style, o its orifice ; in the cavity of the 

 capitate stigma, which is filled with the 

 stigmatic moisture, are pollen-grains 

 putting out their tubes. 



1 On the position of the lobes of the stigma in relation to the placentas in different plants see 

 Brown in Bot. Ztg. 1843, p. 193. 



