REPRODUCTION, VEGETABLE (VEGETABLE OVUM). 



tion (Letters to Simmonds). Barlow, Essays on 

 Surgery and Medicine. Rokitansky, Pathological 

 Anatomy (Hewett's Translation for Sydenham 

 Society). Otto, Compendium of Pathological Ana- 

 tomy "(Trans, by South). Pagct, Lectures oa 

 Nutrition (in Med. Gazette, 1847). Meckel, Ma- 

 nual of Descrip. and Pathological Anatomy. Lever, 

 on Pelvic Tumours (in Guy's Hospital Reports, 

 April, 1842). Velpeau, Traite' des Accouchements. 

 E. Sandifort, De Ankylosi Ossium Pubis. Boyer, 

 Traite' des Mai. Chir. Cooper, Sir A^ Surgical 

 Essays ; in addition to the authors mentioned at the 

 end of the article on the normal and comparative 

 anatomy of the pelvis, and to the various cases 

 cited in the text from the Medico-Chir. Transac- 

 tions, the Edinburgh Journal, the Med. Observ. and 

 Inquiries, and other periodicals. 



(John Wood.) 



REPRODUCTION, VEGETABLE. 

 (VEGETABLE OVUM.) Before the mi- 

 croscope was placed in the hands of the 

 vegetable physiologist, the conditions by 

 which he was surrounded in the investigation 

 of the processes by which the embryo is 

 formed, differed widely from those which exist 

 at present. From the absence of means of 

 observation, the phenomena of reproduction 

 could only be studied in the Phanerogamia. 

 Even as regards the highest cryptogamous 

 plants, very little had been ascertained ; 

 while the Algae and Fungi were involved in 

 the most complete obscurity. But in the 

 Phanerogamia it was already known that two 

 kinds of organs were essential to the produc- 

 tion of the embryo, and something had also 

 been learnt of the mode of their combina- 

 tion. No sooner were these facts established, 

 than, with a readiness of which innumerable 

 examples present themselves in the history of 

 physiological investigations, they were at once 

 seized upon to serve as the ground of a com- 

 parison between the animal and vegetable 

 kingdoms ; and naturalists soon passed to the 

 conclusion that the organs in question were 

 of distinct sexes, or, in other words, stood in 

 the same relation to each other as those of 

 animals. The analogy seemed sufficient for 

 the mind to rest upon ; and the doctrine 

 derived from it was received as indisputable. 



The influence exercised by the state of 

 things we have just described, may be traced 

 in two directions : In the first place, a strong 

 tendency is even now observable in the minds 

 of naturalists, especially in this country, to ap- 

 proach the subject from the same point of 

 departure as before, when the circumstances 

 were so different. The appearance of greater 

 simplicity among the higher plants, was en- 

 tirely dependent on conditions belonging ex- 

 clusively to the observer; that is to say, on 

 the imperfection of the means of observation. 

 Now that so many of these imperfections are 

 removed, to take the Phanerogamia as our 

 starting point in approaching either this or 

 any other general question in vegetable physi- 

 ology, is evidently unreasonable ; we must 

 commence our investigation where there are 

 fewest complications namely, at the unicel- 

 lular plants. From this point we must ascend 

 from class to class, following as closely as may 



211 



be the natural order of complexity of organisa- 

 tion. 



A second result of the same causes is the 

 confusion which so frequently arises in the 

 employment of terms which are derived from 

 the animal kingdom, such as " male," " female," 

 " ovum," &c. As our knowledge of the sub- 

 ject becomes more accurate, the grounds upon 

 which the assumed correspondence between the 

 reproductive organs of plants and animals rests 

 appear less substantial. The only analogies, 

 indeed, which can possess any real value are 

 those occurring between the lowest members 

 of the two series. This is the only point at 

 which the two kingdoms are in mutual contact, 

 and consequently it is here only that an actual 

 correspondence can be traced through succes- 

 sive consecutive modifications. 



The subject of the following article is the 

 origin and development of the germ, or, in 

 other words, the reproduction of plants by 

 means of germs. 



Considering it as a conclusion, respecting 

 which there can remain very little doubt in 

 the present state of vegetable physiology, that 

 every existing plant must have originated as 

 a single cell, there are two modes in which this 

 may be supposed to have taken place. In the 

 one case, a cell originally forming a part of the 

 tissue of the parent, and not previously dis- 

 tinguished in any respect from its neighbours, 

 suddenly assumes a new activity which it did 

 not before possess. To this change the terra 

 C4 Verjiingung," or, as it is rendered by Mr. 

 Henfrey, " rejuvenescence," has been applied, 

 and is most expressive of its nature. A cell 

 in which there has previously been a gradual 

 diminution in the intensity of vital manifesta- 

 tions, recovers the capability of development 

 which it possessed when first formed. Now, 

 however, the formative force by virtue of 

 which the whole subjects the development 

 of all its parts to its own, being abated and 

 weakened by age, the rejuvenescent cell be- 

 comes individualised and is transformed into 

 the rudiment of a new plant, in accordance 

 with a capability of development, which resides 

 entirely in itself. This process is called gem- 

 mation. 



In the other case, the cell from which the 

 new plant originates, manifests from the first 

 moment of its existence conformity to law, 

 on the one hand, in its anatomical relations 

 to the organs of the parent upon which it is 

 supported, or within which it is enclosed, on 

 the other, in the mode in which its develop- 

 ment commences its transformation being 

 the result of an activity inherent in it, not 

 as an individual cell, but as being a part of 

 the parent, and still under the control of its 

 formative force. It is to this cell that the 

 name germ is alone applicable in the restricted 

 sense in which it is generally used ; namely, 

 as expressing not only that it will, if it live long 

 enough, transform itself into an embryo, but 

 that it presents itself uniformly in the same 

 species under the same anatomical condi- 

 tions. 



The term " vegetable ovum," placed at the 



P 2 



