ORGANOGRAPHY. 



open ; or more or less obstructed, as in Orchids (fig. 579, can), 

 or somewhat filled up by a number of very loosely aggre- 

 gated cells (^fig. 581, pp). The walls of the canal also, in all 

 cases, are formed of a loose papillose parenchyma {fig. 581, cc). 

 This canal may be considered as a prolongation of the cavity of 

 the ovary in an upward direction, consequently the loose tissue 

 by which it is surrounded is to be regarded as corresponding 

 to the epidermis of the upper surface of the leaf, merely modi- 

 fied to adapt itself to the peculiar conditions under which it is 

 placed, in the same way as is the case with the epithelium form- 

 ing the lining of the ovary. When the pistil is fully matured, 

 or at the period when it is adapted for receiving the influence of 

 the pollen, the canal of the style becomes further obstructed by 

 a number of lengthened fiUform cells (Jig. 581,/,/), Avhich have 

 been sometimes confounded with pollen-tubes, but from which 

 they are readily distinguished by being twice or three times 

 their diameter. At the period of 

 Fig. 582. Fig. 583. Fig. 584. fecundation, these cells as well as 

 those of the stigma and canal of the 

 style generally, secrete a peculiar 

 viscid fluid containing gum or sugar, 

 or both, called the stigmatic fluid. 

 The loose tissue which thus lines 

 the canal of the style, with the 

 filamentous elongated cells which 

 are developed in it at the period of 

 fecundation, and the secreted fluid, 

 together form a very loose humid 

 tissue, to which the name of con- 

 ducting tissue has been given, be- 

 cause from its loosened nature and 

 nourishing properties it serves to 

 conduct the pollen-tubes down the 

 styles to the ovules, as will be ex- 

 plained hereafter. 



The Stigma. — The tissue of the 

 stigma is analogous to that found 

 in the interior of the style, and 

 just described under tlie name of 

 conducting tissue; in fact, it seems 

 to be nothing more than an expan- 

 sion of tliis externally. It may be 

 either on one side of the style (Jigs. 

 585 and 587), or at its apex 

 (fig. 582), or even on botli sides 

 (jig. 58.3). <^lic position depend- 

 ing upon the point or points 

 where the canal terminates. Its 



A 



Fig. 582. 1. A portion of the pistil 

 of Daphne Lanreola. o. summit 

 of the ovary; t. style terminated 

 by a 8tii,'mu x. '>. a portion of the 

 stigma lilglily mugnified.sliowing 



its paiiillose nature. /•'/.'/. M'A. 



A portion of tlie pistil of I'hin- 

 taijo xiixutilin. o. summit of the 

 ovury; I. style; .1, n. bilateral 

 stigma. The above are from Jus- 



sieu. Fii/. .^H4. Pistil of the 



Periwinkle (Kid'vj). o. ovary; 

 t. style; 8. hairy stigma; d. 

 disk. 



