436 INTRODUCTION TO CYTOLOGY 



as such the exercise of its functions must be governed to a considerable 

 extent by the organism as a whole. 



That it is thus the living system as a whole, and not the individual 

 cell, that is the "primary agent of organization" was definitely main- 

 tained by a number of biologists, who, unable to accept the orthodox 

 cell theory, developed and supported the "organismal theory."^ Accord- 

 ing to this theory, evidence for which was cited in Chapter I, the multi- 

 cellular plant or animal is not a colony or republic of elementary cell 

 individuals but rather a more or less continuous mass of protoplasm 

 which has become incompletely subdivided into subordinate centers of 

 action, the cells, during the course of ontogenesis; the many cells are an 

 accompaniment or a result, rather than the cause, of development and 

 differentiation. In the words of de Bary, "die Pflanze bildet Zellen, 

 nicht die Zelle bildet Pflanzen." The phylogenetic corollary of this 

 theory is that multicellular organisms have evolved not by an aggregation 

 of many individuals but rather by the growth, differentiation, and 

 septation of one, i.e., by just such a process as is observable in ontogeny. 

 This general theory has made slow progress in competition with the 

 descriptively convenient cell theory, but the tendency at the present 

 time is to give it increasing recognition in discussions of the organism and 

 its activity, 



Syngamy and Embryogeny. Plants. — Although it was known to the 

 ancients that there is in plants something corresponding to the sexual 

 reproduction seen in animals, their ideas of the organs and processes 

 involved were very vague. Like Grew and others in the seventeenth 

 century, the botanists of antiquity were aware of the fact that the pollen 

 in some way influences the development of the ovary into a fruit with 

 seeds. That this involves a sexual act was clearly shown by the observa- 

 tions and experiments of R. J. Camerarius (1694), C. Mather (1716, 

 1721), T. Fairchild (1717, 1724), P. Miller (1721), J. Logan (1735), 

 and others,^ but in spite of these and the subsequent researches of J. G. 

 Koelreuter (1761), C. K. Sprengel (1793), and K. F. Gaertner (1849) the 

 idea of sexuality in plants was vigorously opposed in certain quarters for 

 many years. 



An important step in advance was made when G. B. Amici (1830) 

 followed the growth of the pollen tube from the pollen grain on the 



* Here may be mentioned the names of de Bary (1862), Hofmeister (1863, 1867), 

 Sachs (1882), Rauber (1883), Heitzmann (1883), O. Hertwig (1884), Whitman (1893), 

 A. Sedgwick (1894), Heidenhain (1902, 1907), Schlater (1911), Dobell (1911a), Gur- 

 witsch (1913), Ritter (1919), and Rohde (1885 et seq.; see 1923). See the recent 

 discussions by Ritter and Bailey (1928) and Russell (1930). The theory has also 

 been known as the plasma theory, tissue theory, and plasmodial theory. 



^ For an account of these early investigations, see Zirkle (19326). See also Roberts 

 (1929). 



