^M. JORDAN : LETTER TO PROF. CREPIN. 



291 



Upon the whole, the value, as species,3«of social permanent forms of 

 plants is manifestly proved by the single fact of their co-existence sponta- 

 neously in the "same situation. That other forms, which grow isolated and 

 which we are at first tempted to regard as stational varieties, become stable, 

 is equally proved by the single fact of the relation which exists between their 

 distinctive characters and those of the former, 



I have waited for a long time but in vain, for those who are adverse to 

 my opinions, to judge and appreciate the fact of the co-existence, in the same 

 situation, of the most closely allied vegetable forms, and that they should at 

 last give any explanation of it whatever. I always find them suppress and 

 appear totally ignorant of this fact which is annoying to them. This silenee 

 on their part may be expedient and clever, but it also proves their embar- 

 rassment, and shews that they are not very certain in their opinion. After all 

 one cannot for ever ignore a fact which is become notorious — ^palpable ; a fact 

 which strikes the eye of even a slightly serious observer, whose attention is 

 aroused and turned in that direction. Pass through any forest, in the plains, 

 or on the hills, and one cannot but remark the allied forms of the Rabus fruti- 

 eosits, of Linneus growing together pele-mele. Besides, there are those of the 

 old types of the genus Hieracium found growing together in the same locality. 

 Again, we come across those of Tarccxacum offi^cinale, of Draba verna, and 

 many other Linnean types which are unstudied aggregations of species 

 rather than true species. Among the mountains, and above all in the south, 

 where the vegetation is more varied as to species than in the north, although 

 generally less luxuriant and rich in individuals of each species, the law of 

 the distribution of allied species may be observed still more easily. The facts 

 have ^need, doubtless, to be well known and established in order to take 

 account of them ; but when once this is done, their empire in the science 

 will be irresistible ; the systems which are more or less contrary to them 

 must fall or harmonise with them. 



Independantly of the facts which I have indicated and which every 

 observer may easily verify if he will take the trouble, I would advance my 

 own experiments. This I have good right to do, for to them I have given 

 all my time, and I constantly employ three men in the care of a cultivation 

 altogether botanical, exclusively directed to this point — the criticism of 

 species. All this long and expensive labour tends towards this single 

 question — to ascertain whether such and such a vegetable form is distinct or 

 not from such and such others, and to know what constitutes their difier- 

 ences. I endeavour as much as possible in my experiments, to imitate nature 



