Charles Darwin: The Origin of Species by means of Natural Selection

CHAPTER IX. HYBRIDISM.
5. RECIPROCAL DIMORPHISM AND TRIMORPHISM. (continued)

We may, however, infer as probable from the consideration of dimorphic and trimorphic plants, that the sterility of distinct species when crossed and of their hybrid progeny, depends exclusively on the nature of their sexual elements, and not on any difference in their structure or general constitution. We are also led to this same conclusion by considering reciprocal crosses, in which the male of one species cannot be united, or can be united with great difficulty, with the female of a second species, while the converse cross can be effected with perfect facility. That excellent observer, Gartner, likewise concluded that species when crossed are sterile owing to differences confined to their reproductive systems.

This is page 297 of 505. [Mark this Page]
Mark any page to add this title to Your Bookshelf. (0 / 10 books on shelf)
Customize text appearance:
Color: A A A A A   Font: Aa Aa   Size: 1 2 3 4 5   Defaults
(c) 2003-2012 LiteraturePage.com and Michael Moncur. All rights reserved.
For information about public domain texts appearing here, read the copyright information and disclaimer.