6.8 



BOTANY. 



Vegetable and the blossoms do not appear till aufumn ; ' but a 

 Physiology. ( ; ue examination will readily ascertain, that the seed- 

 "." k l]( j formed in autumn is the very same which cornea 

 to maturity in the following spring." " A pine 

 apple," adds this agreeable writer, " was once very 

 unexpectedly cited to me as an instance of fruit be- 

 ing formed before the flower, because the green 

 fruit, in that instance as in many others, is almost 

 fully grown before the flowers expand. The seeds, 

 however, the essence of Ike fruit, are only in em- 

 bryo at this period; Just as in the germcn of an 

 apple blossom." All nowers are furnished with both 

 stamens and pistils, in the same individual, or in 

 two distinct individuals of the same species. This 

 fact has been ascertained in the most minute ex- 

 amples, even in mosses, which were long supposed 

 anomalous. Ferns form the only apparent excep- 

 tion ; and it is highly probable, from general ana- 

 logy, that these parts, though still concealed, have 

 existence in that order. Although plants have 

 sometimes abortive stamens, and barren pistils, yet 

 the whole will not be found to be unproductive ; on 

 the contrary, there will always be a certain number 

 to accomplish the propagation of the species. Na- 

 ture, too, admirably provides for the commixture of 

 the pollen with the fluid covering the stigma, by a 

 synchronous operation of the parts themselves, or by 

 other agents to be hereafter noticed. The most de- 

 cisive proof of the necessary agency of the stamen 

 on the pistil for the production of the perfect fruit, 

 is afforded by the very well known experiment, 

 " made in 17-49 upon a palm tree at Berlin, which, 

 for want of pollen, had never brought any fruit to 

 perfection. A branch of barren flowers was sent by 

 the post from Leipsic, twenty German miles distant, 

 and suspended over the pistils. Consequently abun- 

 dance of fruit was ripened, and many young plants 

 raised from the seeds." Linnaeus further encoun- 

 tered all the cavils and objections of his opponents, 

 by accurate and satisfactory experiments : But, as is 

 the case too commonly in philosophical warfare, he 

 refuted, but could not always silence clamour. 



It was urged by Pontedera and Tournefort, that 

 the pollen was a mere excrement ; but various argu- 

 ments were adduced against this opinion as well as 

 the other, which was also entertained fay these philo- 

 sophers, of the circulation from the stamens of a cer- 

 tain secreted something to the seeds ; but Linnaeus 

 decided both points by experiment. " He removed 

 the anthers from a flower of Glaucium pficeiticiiim, 

 stripping off the rest of that day's blossoms. An- 

 other morning he repeated the same practice, only 

 sprinkling the stigma of that blossom, which he had 

 last deprived of its own stamens, with the pollen from 

 another. The flower first mutilated produced no 

 fruit, but the second afforded very perfect seed. My 

 design," says Linnreus, " was to prevent any one in 

 future from believing, that the removal of the anthers- 

 from a flower was in itself capable of rendering the 

 germen abortive." 



It is very remarkable, that the stamens are always 

 shorter than the pistils in drooping flowers, and long- 

 er in erect ones. Evidently destined to favour the 

 influence of the pollen. 



Many other curious and beautiful means are em- 



ployed, to promote the due application of the pollen Vegetab: 

 to the stigma. In some plants, such as the Partiassia, ^hysiolog 

 the stamens successively lean over the stigma, and de- ^~ < y^T 

 posit the pollen. Others have a spontaneous motion. p, paga- 

 Others are connected by a membrane, which con- tion. 

 tracts or dilates according to the state of the atmo- 

 jphere. Other stamens possess a considerable elas- 

 ticity, by which means the pollen is projected upon 

 the stigma. In other flowers, the germen has a con- 

 siderable curvature endowed with an elasticity, that 

 brings it into contact with the stamens. The sta- 

 mens of the Barberry possess a high degree of irrita- 

 bility, which has been very particularly described by 

 Dr Smith and Mrs Ibbetson, and, by means of that 

 property, the ends of vegetation are attained. 



" In this" flower, says Dr Smith, " the six sta- 

 mens, spreading moderately, are sheltered under the 

 concave lips of the petals, till some extraneous body, 

 as the feet or trunk of an insect, in search of honey, 

 touches the inner part of each filament near the bot- 

 tom. The irritability of that part is such, that the 

 filament immediately contracts there, and, conse- 

 quently, strikes its anther, full of pollen, against the 

 stigma. Any other part of the filament may be 

 touched without this effect, provided no concussion 

 be given to the whole. After a while the filament 

 retires gradually, and may again be stimulated ; and 

 when each petal, with its annexed filament, is fallen 

 to the ground, the latter, on being touched, shews as- 

 much sensibility as ever." 



The economy of aquatic plants is beautifully adapt- 

 ed, to the same purpose. Many of them lie beneath, 

 the surface of the water until the flowering season, 

 when they shoot forth their flowering spikes, so that 

 the flowers are completely exposed above the water, 

 and as soon as the seed is formed, it sinks to the bot- 

 tom. The rising and falling, opening and closing of 

 the nymphsea, is known to all that have been in the 

 habits of observing that plant ; and the Vnlisneria 

 spiralis (Plate LXXIV.) exhibits some beautiful PLATS 

 phenomena of the same kind. LXXIV. 



This plant grows in ditches in Italy, and its fer- 

 tile flowers grow on spiral stalks, which, by uncoil- 

 ing, allow the flowers to rise to the surface, where 

 they expand. Barren flowers are, during this time, 

 formed at the bottom, on a distinct root, and rise al- 

 so to the surface in great abundance. By this means 

 the pollen is scattered over the first flowers, which, 

 after impregnation, sink, and the fruit reaches matu- 

 rity at the bottom. 



Insects are very frequently the agents of the ferti- 

 lization of the stigma. Kotlreuter and Sprengcl 

 have made many valuable observations on this fact. 

 The latter of these gentlemen had both leisure and 

 patience enough to examine the manner in which in- 

 sects perform the office of impregnation. He found, 

 that various species of bees, and many flying insects, 

 are employed ; and he further learnt, that some flow- 

 ers have insects peculiar to themselves. The object 

 of the animal is" to obtain honey, and while in quest 

 of it, his hairy body collects the pollen from the male 

 flower, and communicates its influence to the female 

 during some subsequent search. It is not a little 

 singular, that those insects which are not confined to 

 a particular species, fix upon one species during the 



