432 



Scientific Intelligence. 



" The most numerous, the most important, and often the most anoma- 

 lous facts in the existing distribution of plants, are explained by the ope- 

 ration of causes anterior to those now in operation, or by the joint opera- 

 tion of these and of still more ancient causes, sometimes of such as are 

 primitive (connected with the earliest condition of the planet). The 

 geographical and physical operations of our own epoch play but a second- 

 ary part. I have shown that in starting from an original fact, which it 

 is impossible to understand, of the creation of a certain form, in a certain 

 country, and at a certain time, we ought to be able, and sometimes are 

 able, to explain the following facts, chiefly by causes that operated pre- 

 vious to our own epoch : — 1, the very unequal areas occupied by Nat- 

 ural Orders, Genera, and Species ; 2, the disconnection of the areas 

 that some of the species inhabit ; 3, the distribution of the species of a 

 genus or family in the area occupied by the genus or family; 4, the differ- 

 ences between the vegetations of countries that have analogous climates 

 and that are not far apart, and the resemblance between the vegetation of 

 countries that are apart, but between which an interchange of plants is 

 now impossible. 



" The only phenomena explicable by existing circumstances, are — 1, the 

 limitation of species, and consequently of genera and families, in every 

 country where they now appear ; 2, the distribution cf the individuals of 

 a species in the country it inhabits ; 3, the geographical origin and exten- 

 sion of cultivated species; 4, the naturalization of species and the oppo- 

 site phenomenon of their increasing rarity ; 5, the disappearance of species 

 contemporaneous with man. 



"In all this we observe proofs of the greater influence of primitive causes, 

 and of those anterior to our epoch ; but the growing activity of man is 

 daily effacing these, and it is no small advantage of our progressing civi- 

 lization that it enables us to collect a multitude of facts of which our 

 successors will have no visible and tangible proof." 



An Appendix, indicating the researches now needed for the advance- 

 ment of Geographical-Botanical science, under several heads, addressed 

 respectively to physicists and meteorologists, to geographers, to geologists, 

 to vegetable physiologists, descriptive and travelling botanists, and to 

 philologists, brings these most interesting volumes to a conclusion. 



Our present object is to call the attention of American naturalists and 

 natural philosophers to this work, not to criticise it. That would require 

 much consideration and a wider range of knowledge than we can pretend 

 to. There are, however, several topics upon which we are inclined to 

 venture a few remarks, as fitting opportunities occur. a. g. 



2. Origin of the Embryo in Plants. — Die Befruchtung der Phanero- 

 gamien, Leipsic, 4to, 1856, is the title of a new and important memoir by 

 a young investigator, Dr. Radlkofer, of Munich ; whose name bids fair to 

 be celebrated for having terminated by his investigations the great con- 

 troversy of our day in vegetable reproduction, namely, the respective 

 functions of the pollen and the ovulum. Our notice in the July number 

 of the Journal, recorded the recent history of investigations in this depart- 

 ment, as far as then known to us. We now learn that the Schleidenian 

 view, viz : that the embryo is formed of (or in) the extremity of the pollen- 

 tube, — has at length been definitely abandoned, both by its author, and 



