4 INTRODUCTION TO EMBRYOLOGY OF ANGIOSPERMS 



inside it, but eventually he lost sight of them and could not say 

 whether they returned to the grain, entered the stigma, or dissolved 

 away in some manner. 



Amici's discovery stimulated the young French botanist Brong- 

 niart (1827) to examine a large number of pollinated pistils with a 

 view to understanding the interaction between the pollen and the 

 stigma and the introduction of the fertilizing substance into the 

 ovule. He found the formation of the pollen tubes (he called them 

 "spermatic tubules") to be a very frequent occurrence but per- 

 suaded himself to believe that, after penetrating the stigma, the 

 tubes burst and discharged their granular contents, which he likened 

 to the spermatozoids of animals and considered to be the active part 

 of the pollen. He thought he saw these "spermatic granules" vi- 

 brating down the whole length of the style and entering the placenta 

 and ovule, and he drew a series of figures to illustrate the whole 

 process. In appreciation of this work, Brongniart was awarded a 

 prize by the Paris Academy of Sciences and recommended for ad- 

 mission to the Academy. 



Amici (1830) applied himself once again to the problem, studying 

 Portulaca oleracea, Hibiscus syriacus, and other plants, and wrote a 

 letter to Mirbel in which he put the following question: "Is the 

 prolific humor passed out into the interstices of the transmitting 

 tissue of the style, as Brongniart has seen and drawn it, to be trans- 

 ported afterwards to the ovule, or is it that the pollen tubes elongate 

 bit by bit and finally come in contact with the ovules, one tube for 

 each ovule?" His observations completely ruled out the first 

 alternative, and he definitely concluded in favor of the second. 



About the same time, Robert Brown (1831, 1833) saw pollen grains 

 on the stigmas and pollen tubes in the ovaries of certain orchids and 

 asclepiads but was uncertain as to whether the tubes were always 

 connected with the pollen grains. He thought instead that, at least 

 in some cases, the tubes arose within the style itself, although pos- 

 sibly they were stimulated to develop in consequence of the pollina- 

 tion of the stigma. 2 



Schleiden's Theory of the Origin of the Embryo. Meanwhile 

 other workers also became interested in the problem, and in 1837 

 Schleiden published some very detailed observations on the origin 



2 It now seems that Brown was at times confusing pollen tubes with the elon- 

 gated cells of the transmitting tissue in the style. 



