MONOGRAPH OF THE GENUS PYRUS. 187 



pears, may have more interest for the horticulturist. But the 

 present attracts the special attention of the scientific botanist. 



As stated in the Introduction, Professor Decaisne entered 

 upon his great undertaking more than twenty years ago, when, 

 in the year 1850, he became the Professor of Culture. He 

 cites the instructions under which the separate collection of 

 fruit-trees was constituted, and the professor of culture was 

 charged with its management, and was directed to bring to- 

 gether all the known varieties, with all their names, " afin 

 d'etablir une uniformite de nomenclature necessaire pour 

 toutes les parties de la Eepublique." This is a decree of the 

 National Convention, June 10, 1793. The collection which 

 Decaisne has so diligently and acutely studied actually dates 

 from the year 1792, when the fruit-garden of the Chartreux 

 of Paris was broken up, and two trees of each variety trans- 

 ported to the Jardin des Plantes. In 1793 it contained 185 

 varieties. In 1824, when Thouin died, there were in it 265 

 varieties of pears alone ; it has now more than 1400 varieties 

 of this fruit. It is interesting and important to know that 

 the collection still preserves the greater portion of the very 

 types described a century ago by Duhamel, For seven years 

 Professor Decaisne studied the incomparable collection under 

 his charge, making drawings and analyses, in which he is so 

 skilful, and an herbarium of their flowers and foliage, before 

 he commenced the publication of the " Jardin Fruitier du 

 Museum," which he is now bringing to a close. 



As to giving a correct nomenclature and available charac- 

 ters, this is difficult enough, as all botanists know, for the 

 species themselves (which must needs have, or be assumed to 

 have, real distinctions) in any large genus, such as Quercus, 

 Rosa, Rubus, and the like ; how much more difficult, even to 

 impossibility, it must be in the case of cultivated varieties, of 

 ever increasing numbers, usually named without system, some- 

 times of mixed origin, and often too like each other to be dis- 

 tinguished by any available descriptions. Here colored plates 

 are a necessity ; and those of this great standard work, upon 

 which no pains have been spared, leave little to be desired 

 that art can supply. 



