10 



The Journal of Heredity 



M \l.i: I LOWKK Ol MM/i: 



The corn lassel is made up of many 

 slender branches of small flowers, 

 each with a i)air of light yellow 

 stamens hung on very slender fila- 

 ments. From these stamens, half a 

 dozen of which are seen extruded in 

 the photogra])h, the jjollen is dusted 

 by tile wind on the corn silk protrud- 

 ing from the husk at some jjoint on 

 the stalk below. This silk consists 

 of long, slender stigmas (female); a 

 ])ollen grain falls on the end of each 

 one of these and must grow down the 

 whnlf length of the silk to reach its 

 own i)arti(ular ovule on the car, 

 which it fertilizes to produce a 

 grain of corn. Photograph highly 

 enlarged. (Fig. 6.) 



"Solchc Praparate sind ohiic Zweifcl 

 atis dcii Kopf gczcichnct." 



Ilofmeistcr, from the beginning of 

 his study of fertilization in seed plants, 

 had sought in the pollen tulje for some 

 ecjuivalcnt of the spermatozoids, those 

 motile male cells of the mosses and 

 ferns that had first been understood by 

 linger in 1837. He was unable, how- 

 ever, to do more than point out the 

 mistake of earlier observers in regard- 

 ing the starch grains of the pollen tube 

 as s]jermatozoids, and to suggest the 

 likelihood that these motile cells might 

 be discovered in the gymnosperms, a 

 prediction the fulfilment of which was 

 realized by Ikeno and Webber 50 years 

 later. In his study of pollen tubes 

 Hofmeister demonstrated to his own 

 satisfaction that the tube does not open 

 in accomi)lishing fertilization. His view, 

 which was the one ctirrent till 1884, was 

 that the egg is stimtilated to develop 

 into the embryo by some substance 

 that difftises through the imperforate 

 wall of the ])ollen tube. 



DISCOVERY OF PROTOPLASMIC FUSION. 



We come now to consider a series of 

 discoveries of supreme importance in 

 the investigating of the essential sexual 

 l)r()cess in jjlants. This is the ])eriod in 

 which the problem that had bafiled 

 naturalists for twenty centttries was at 

 last solved, at least in one most essential 

 feature, by the demonstration of the 

 occurrence at fertilization of a mingling 

 of ])aternal and maternal substances. 



It will not be without interest at this 

 ])oint to note the intellectual stimuli 

 which led an unustial number of workers 

 to investigate this ])hase of our jjroblem. 



In the first ])lace, there were on 

 record, and under discttssion, at the 

 middle of last century, the many ptizzling 

 observations of the "vSpiralfaden," or 

 animalcuhc. as they were thought to be, 

 that had been found arising from a 

 number of plants. These motile, spiral 

 filaments had been seen in a liverwort 

 (Fossotnbromia) by Schmiedel (1747), 

 in Splnij^nunt by Esenbeck (1822), in 

 Cham by BischoiT (1828). and liiudly, on 

 the fern ])rothallus by Xaegeli (1844). 

 Unger (1834-v?7) sttulieil these bodies in 



