598 



SUPPLEMENT 



of great interest to the microscopic observer. 

 Plate 34, fig. 28, is the pollen of the marsh- 

 mallow, consisting of small globes thickly 

 studded with prickles. 'These atoms are not, 

 however, the actual farina ; for on examination 

 with deep powers they are found to be delicate 

 little bags, containing an inconceivably fine 

 powder, the true vegetable semen. The pistil 

 is the next object for observation : it consists 

 of three parts, the germen, the style, and the 

 stigma. The style is a hollow tube, forming 

 a communication between the olher parts of the 

 pistil ; the stigma is usually a small bulbous 

 substance supported by the style ; and the 

 germen is the lower extremity of the pistil, 

 reposing within the corolla of the flower. At 

 the time of fecundation the farina falls on the 

 stigma^ whence it is presumed to pass through 

 the style to the germen, the seeds in which 

 thus become impregnated and indued with 

 vegetable vitality. The stigma in some 

 flowers is either divided, or has a small open- 

 ing which contracts and expands at intervals ; 

 in others this organ exhibits a porous surface ; 

 in either case it is suitably constructed for the 

 office it fulfils. The germen is the most re- 

 markable part of the pistil, answering to the 

 ovaries in animals. If the outer covering be 

 carefully removed, the seeds will be discovered, 

 clustered like grapes, and a considerable dif- 

 ference of formation will be observed in the 

 germen of different flowers. We have here 

 slightly glanced at a few leading facts elicited 

 from a microscopic examination of blossoms ; 

 and in connection with them, we would men- 

 tion the singular means by which the impreg- 

 nation of the pistil by the farina is frequently 

 effected Some flowers are hermaphrodite, 

 and contain within themselves both the male 

 and female organs of reproduction ; others are 

 either male or female. " The motion which 

 is observed at the time of impregnation in 

 those flowers which unite the sexes is very 

 remarkable : thus, for example, the stamina of 

 the common barberry, when touched on their 

 inner side, (that turned towards the germen) 

 as may happen when an insect settles on 

 the flower, to suck the honey from its basis, 

 suddenly move inwards, and strike their 

 anthers against the stigma, by that means 

 effecting the fecundation." When (he organs 

 are in separate flowers, and, as is the case 

 with the hop, hemp, &c.,on different plants, 

 the farina will frequently be carried from the 

 stamen of the male flower to the stigma of 

 the female, by the honey bee, which visits 

 the various blossoms to collect their sweetness, 

 and almost invariably bears away on its wings 

 and body a portion of the farina from one 

 flower, and unconsciously deposits it on the 

 stigma of another. There arc olher means of 

 impregnation in these cases, more obvious; 



such as the agency of the wind, or the actual 

 deposition by the florist of the farina on the fe- 

 male organ. 



When the impregnation of the germen is 

 effected, all the superfluous parts of the plant 

 fall off, and the former increases in size till 

 the seeds contained in it have reached matu- 

 rity. " The form, as well of the different 

 seeds, as of the coverings in which they are 

 inclosed, is as various as that of the flowers, 

 and adapted in the most admirable manner to 

 the preservation of the species as regards their 

 extended dispersion, their security, &c. The 

 provision, too, is remarkable, by means of 

 which, whatever may be their position in the 

 ground, when they germinate, they invariably 

 shoot their radicle downwards, and the plumula 

 upwards." The principal parts of a seed are the 

 cotyledons, or seed-lobes, which after germina- 

 tion become leaves, and the corculum or heart, 

 consisting of the radicle and the plumula. Seeds 

 require, in general, to be prepared for micro- 

 scopic examination, by steeping them in hot 

 water, when the several parts just named separ- 

 ate and discover their respective formations. 

 The exterior of many seeds is, however, so re- 

 markable, that without any preparation they are 

 most interesting objects under every power Unit 

 will afford light sufficient to develope their 

 structure. To attempt a description of all the 

 varieties, is impossible; we must simply refer to 

 some of their singular appendages, and des- 

 cribe a few whose formation is most striking. 



The pappus, or down, with which many 

 seeds are provided is a wonderful characteristic, 

 whether we regard the structure of the down 

 itself, or the ends it is intended to serve. 

 Plate 34, fig. 9, exhibits a filament of thistle 

 down, as it appears under a linear magnify- 

 ing power of 80. This down, with some 

 variety of form, is either placed on the top of 

 seeds in the manner of a crown, or on each 

 side like wings, or it covers the entire surface ; 

 in any case the purpose is much the same, 

 namely, to provide the seed with means of 

 transit from the seed-case to the spot of earth 

 on which it is destined to fall and germinate. 

 And to this wonderful contrivance of nature 

 for the propagation of vegetable life, we are 

 to attribute much of the verdure and floral 

 loveliness of those wild, sequestered spots, 

 where the cultivating hand of man has never 

 been employed, and where the human foot 

 has rarely trod. The down is sometimes 

 designed as a protection to the seed ; it either 

 repels the moisture which would injure it, or 

 prevents undue pressurefromconliguousbodies. 

 And in some cases, it is so disposed, that it not 

 only directs the seed into a proper position for 

 germination, but also, if the seed be placed in 

 the earth with its plumula downwards, will 

 work it up to the surface again, and re -de- 



