26 
a general way as (1) Biological Relationships, (2) Morphological 
and Physiological Features, (3) Economic Applications, (4) Geo- 
graphical Distribution, (5) Aesthetic and Landscape Features, 
Practical considerations enter largely into groupings of any kind. 
. Biological Relationships. — \n this installation it is sought to 
one species of the various plant families in juxtaposition, 
the groups thus formed being located in relation to each other in 
some predetermined sequence ; this sequence in recently planted 
botanical gardens is usually one which seeks to demonstrate not 
alone affinity, but the progressive increase in floral complexity, in 
other words, an evolutionary sequence. In such installations 
practical considerations render the sequence necessarily incom- 
plete in any one set of plantations ; sunshine-requiring herbaceous 
plants and shrubs cannot be successfully grown close to trees, 
and some natural families, such as Papilionaceae and Rubiaceae 
contain herbs, shrubs and trees ; climatic considerations prevent 
many families being brought into any one sequence; the biologi- 
cal grouping must then be obtained piecemeal ; the most satis- 
factory and least expensive method is to grow the collections of 
trees (arboretum), of shrubs (fruticetum), of vines (viticetum), and 
of herbaceous plants, for the most part, at least, in separate areas; 
families principally composed of plants inhabiting climates other 
than that of the locality require artificial environment, such as 
glass houses for tropical and warm-temperate zone plants in 
gardens of the cold-temperate zone ; it would be an interesting 
experiment to ascertain if arctic plants could be grown success- 
fully in the temperate zones by some system of refrigeration. 
By a suitable arrangement of land and water, aquatic plants may 
be brought to some extent into juxtaposition with those of the 
same or related families requiring dry soil. One advantage in 
the biological grouping of large collections is the facility with 
te 
By indicating on the labels the native regions of slants biologi- 
cally grouped, much simple information bearing on geographical 
