Researches in Vegetahle Physiology. 233 



stem in the form of starch, and thus passes towards the buds. 

 Subsequently the starch produced in the leaves descends along 

 the stem in the form of starch itself or of sugar; and it is only 

 on its arrival in the root that it takes on the form of inuline. 



III. 



We cannot conclude this revision of the principal recent 

 physiological publications witliout casting a glance upon a 

 group of very interesting works, although these do not yet allow 

 us to rise to general conclusions. We would speak of fecunda- 

 tion in phanerogamous plants, and the part which insects per- 

 form in it. The idea itself is not new ; and even a century 

 ago Sprengel* cited numerous cases of flowers fecundated by 

 the mediation of insects. But it is only in our time that it has 

 been attempted to generalize these facts ; and Mr. Darwin was 

 the first to put forwai'd the notion that the fecundation of a 

 flower by itself is contrary to the laws of nature, and that the 

 reproduction of a species is not well assured except by cross- 

 ings between different individuals. 



A theory like this cannot of course be proved except by di- 

 rect investigation of facts ,' and the facts, when we have to do 

 with fecundation, are most minute, and demand peculiarly in- 

 genious and patient observations. Several naturalists have 

 advanced to the breach ; and we possess a fine collection of 

 special memoirs, the conclusions from which already form a 

 solid basis for theoretical ideas. However, if the observers 

 have had to manifest great patience, the recompense waited for 

 them at the end. Nothing is more curious than the details of 

 organization by which spontaneous fecundation, apparently so 

 easy, is rendered useless or even impossible. The researches 

 of Mr. Darwin" himself upon the fecundation of the Orchids, 

 upon the dimorphism of the primrose, and upon the trimorphism 

 of Lythrum salicaria are well known. He has found imitators 

 in MM. Hildebrandt and Delpino. Both these authors have 

 published numerous memoirs, sometimes studying thoroughly 

 all the details of fecundation in a certain plant or family, some- 

 times tracing throughout the vegetable kingdom a certain type 

 of fecundation, and pointing it out wherever it is manifested. 

 M. Hildebrandt f, moreover, some time since, brought toge- 

 ther all the data we possess upon the subject, and endeavoured 

 to group them methodically. The perfectly uniform conclusion 

 of all these works is, that in the great majority (if not in the 

 totality) of plants direct and spontaneous fecundation is im- 



* Das entdeckte Geheimniss der Natur im Bau imd Befruchtung der 

 Blunien. Berlin, 1793. 

 t Die Geschlecliter-Vertlieilung bei den Pflanzen. Leipzig, 1867. 



