ESSENTIAL OEGANS — THE STIGMA. 



249 



stigma consists of loose cellular tissue, and secretes a viscid matter 

 ■which detains the pollen, and causes it to protrude tubes. This 

 secreting portion is, strictly speaking, the true stigma, but the name 

 is generally applied to all the divisions of the style on which the 

 stigmatic apparatus is situated, as in Labiatse. The stigma alternates 

 with the dissepiments of a syncarpous pistil, or, in other words, 

 corresponds with the back of the loculaments ; but ia some cases it 

 would appear that half the stigma of one carpel unites with half that 

 of the contiguous carpel, and thus the stigma is opposite the dissepi- 

 ments, that is, alternates with the loculaments. This appears to be 

 the case in the Poppy, where the stigma of a single carpel is two-lobed, 

 and the lobes are opposite the septa. 



If the stigma is viewed as essentially a prolongation of the 

 placenta, then there is no necessary alternation between it and the 

 placenta, both being formed by the margins of carpellary leaves, which 

 in the one case are ovuliferous, in the other stigmatiferous. There is 

 often a notch in one side of a stigma (as in some Kosaceas), indicating 

 apparently that it is a double organ like the placenta. To the division 

 of a compound stigma the terms bifid, trifid, etc., are applied, accord- 

 ing to the number of the divisions. Thus, in Labiatse (fig. 324), and 

 in Oompositse (figs. 326, 438 s), the stigma is bifid ; in Polemonium, 

 trifid. When the divisions are large, they are called lobes, and when 

 flattened like bands, lamelke; so that stigmas may be bilobaie, trilobate, 

 bilamellar, trilamellar, etc. 



It has already been stated that the divisions of the stigma mark 

 the number of carpels which are united together. Thus, in Cam- 

 panula (fig., 440), the quinquefid or five-cleft stigmia indicates 



flllW 



Pig. 440. Kg. 441. Fig. 442. Pig. 443. Fig. 444. 



five carpels, the stigmata of which are separate, although the other 

 parts are united. In Bignoniacese (fig. 441), as well as in Scrophu- 



Pig. 440. Stigmas, s, of Campanula rotundifolia. I, Style. Fig. 441, Bilamellar stigmas 

 of-Bignonia pandorea. The two lamellae are applied naturally against each other in 1, while 

 in 2 they are artificially separated. Fig. 442. Globular stigma of Mirabilis Jalapa. t, Style, 

 s. Stigma, Pig. 443. Circular stigma, s, and (, style of Arbutus Andrachne. Fig. 444. 

 Pistil, of Papaver somniferam, or opium Poppy, o, Ovary, s, Eadiating stigmas on its 

 summit. ^ 



