1895.] Present Problems in the Cactacee. 219 
known, different students having placed them in very differ- 
ent positions. If a form is found which will give the transi- 
tion to some known family, it will probably be a Peireskia- 
like species growing in the forests of north-western Brazil. 
All evidence goes to prove the newness of the family, such 
as their great variability, their lack of sharp divisions be- 
tween the species and the genera, the large size of some of 
the latter, the constancy in the structure of the flowers, great 
similarity in the seedlings, similar characteristics of the axil- 
lary vegetative points (differences being derivable by slight 
modifications in degree), practical confinement in range to a 
single continent though a very large family, perhaps also 
their very ‘‘vitality,” already referred to, including possibility 
of free grafting and hybridizing. 
The study of the development of the flower may give a clue 
to affinities. Their geographical distribution is imperfectly 
known. It is worth observing how closely this follows the 
line of newer mountain chains on the American continent— 
extending along the Andes and in Brazil to Venezuela through 
the West Indies to Mexico and northward into the United 
States. 26 
So much for some of the special questions which, by those 
who can study the plants in the field or who can command 
the proper material, should be solvable. In addition to 
these, certain unusually marked characteristics of 
Cactacex, in particular their variability, the perfection of 
their adaptations, and their segregation into many species 
under a simple environment, make it seem that they are par- 
ticularly fitted to contribute to the solution of more general 
Problems. As to all of these points, variation, historical 
development of adaptations, and causes of segregation into 
Species, the old questions remain yet to be answered. Is 
there or is there not an innate tendency in living matter to 
variation, or is variation in some unexplained way induced by 
the surroundings? In the former case, is variation a function 
of living matter, co-originating with it, or has it been ac- 
quired by selection or otherwise, since it gives such good 
results ? In either case, does variation tend of itse!f to follow 
Certain lines, or is it ‘‘ fortuitous?” In the former case, are 
the lines of th l dapti ar in different 
directions, natural selection cutting off the unfit and leaving 
+ Pm ro 
Ly evapety. 
** See the map in Neumayer, Erdgeschichte, 2: 655. 
