106 
Nr. 2. C. H. OSTENFELD and C. SYRACH LARSEN: 
far west as from Lake Baikal northwards; L. sibirica in 
the area west of L. Gmelini as far west as N. E. Europe. 
The differences between the species and their variability 
have been considered under each species, and their 
synonymy and the records of specimens upon which 
our conclusions are based are cited in full. The geo- 
graphical varieties of L. Gmelini, namely L. olgensis and 
L. Principis Rupprechtii, form a kind of transition to the 
first-named sub-genus, and their areas of occurrence 
also cause them to approach the Chinese species of that 
sub-genus. 
The variety of L. decidua, var. polonica, is a link between 
that species and L. sibirica, and is a form which appears 
to be not far from extinction. 
The species of the second sub-genus are of importance 
as forest trees, and several of them are objects of 
extensive cultivation. 
Between the species which meet in nature, hybrids are 
found as regards the combination L. Gmelini X sibirica, 
while the combinations L. Lyallii X occidentalis and L. 
Mastersiana X Potanini have not yet been recognised. 
When cultivation brings two species together, hybrids 
also arise. L. decidua X laricina has been known for a 
very long time, but is usually misinterpreted; L. Kaempferi 
x decidua is much more recent, but seems to be of 
economic value, and will probably become much 
commoner; L. Kaempferi X sibirica has been reported, 
but is not definite. 
When L. Gmelini becomes more used in cultivation, 
this most valuable species will no doubt hybridise with 
several of the other species. 
