210 



UN NATUKAL HYBRIDS. 



assistance m the way of living roots wherewith to experiment, or 

 for other help. On one point I would remark :— Given a wood 

 containing a wind-fertilised monoicous shrub, and a fairly-marked 

 variety of the same, there are few botanists but would expect to 

 find them accompanied by innumerable hybrids showing every 

 intermediate state. Such hybrids, however, are not of the grade 

 which makes them much worth naming, but it is always interesting 

 to know that a species will cross with its variety, as is probably the 

 ease in this instance, since a few cases to the contrary are ou 

 record. As a matter of fact, the number of natural hybrids recorded 

 between species and their varieties is small indeed compared with 

 that recorded between plants which are generally accepted by 

 botanists as distinct species. 



A paper dealing with hybrids, but omitting all allusion to the 

 phenomenon of sterility, is a distinct novelty ; and the time seems 

 a fitting one wherein to recapitulate briefly a few of the main 

 facts known to us concerning Hybridity, as well as to suggest what 

 assumptions we are entitled to make on the basis of the knowledge 

 aftorded by these ascertained facts. I shall deal chiefly with sterile 

 hybrids, because, until these are understood and admitted, it is 

 useless to attack the much more difficult and complicated question 

 of the fertile hybrids. But a word with regard to Sterility :— I very 

 much doubt whether there is any permanent sterility among 

 Phanerogams, except such as is due to hybridity. A plant may 

 fail to fruit owing to its environment ; it may be able to live and 

 thrive and flower, but its present habitat may be too hot or too 

 cold too wet or too dry, to permit of its fruiting ; but this state can 

 nardly be considered as other than dependent on the temporary 

 conditions. A plant may be temporarily unfruitful through disease. 

 Again, some plants, especially such as are either actually or func- 

 tionally monoicous or dioicous, not unfrequently fail to produce 

 n-uit simply because they have not been fertilised; but this is 

 merely virginity, it is not sterility. 



With regard to what we know to be absolute facts, I presume it 

 will be admitted by all that we know that two distinct species, that 

 is, two species which are not connected by intermediates, may in 

 many cases be artificially cross-fertilised ; that fertile seed may 

 result ; that the plants springing from such seed will usually present 

 external characters more or less intermediate to the two parents ; 

 tnat in being commonly entirely or partially sterile they present a 

 totally new character not common to either parent ! But there are 

 also some things that we do not know ; I think I may fairly say 

 tuat we do not know of any two distinct species (like, for example, 

 Uola camna and V. Rimniana) which, when growing alone under 

 tneir normal environment,* are without any tendency to approach 



H*™/^ ay ^!' Under , their norm al environment" advisedly, because under 

 SS,pS^?T F lantS - ° ften assume temporary states resembling other 

 « mZ fit / ™ SpeC1 t ; th - US the state of R^nculm kederaceus called 

 Le% r Z"d??-K ,T? Wb p* Sil ^ lat - eS S - L ' nor »"» ldi ; the land state of E. 

 f1?i hhu, ,-• lutar " l i Revel? Emulates R. intermedins; the state of 

 Epdobutm montanum called « forma aprica » simulates E. Durim ; the state of 

 Wroannnn nmpU* called « var. lengUrima " simulates!?, affine, and so on 



