THE PLANT WORLD. 
2 
puzzle us in our treatment of plants in the garden; and its right 
appreciation should afford helpful guidance to methods of cul¬ 
tivation. 
Can Nature Guide Horticulture? —The amount of truth in 
the statement that horticulture as an empirical art can obtain 
but little guidance from botany and a knowledge of the condi¬ 
tions under which plants occur in nature, depends upon the de¬ 
gree of our ignorance of the influence of environmental factors 
and^iof the relationships of plants to them, and of our grasp of 
physiological as distinct from physical effects. With increase of 
knowledge the validity of the statement must decrease. In no 
direction has research in recent years provided more valuable data 
of significance to horticulture than in that of the water-relation¬ 
ships of plants—the conception of physiological drought is far- 
reaching. 
Soils and Physiological Drought. —Our knowledge of the me¬ 
chanical and chemical states of soils, of their varying retentive¬ 
ness of water, and of the effect upon this of aeration and tem¬ 
perature, tells us that soils, anatomically and constitutionally dif¬ 
ferent, may be physiologically alike in respect of the water- 
relationships of plants. It sounds paradoxical to say that a soak¬ 
ing peat-soil is to plants in respect of water like a desert-sand, a 
salt-strand, a tufa, a half-frozen loam, a tree-bark. Yet all are 
physiologically dry to the plant—a critical item of botanical in¬ 
formation to the gardener. 
Plant-form as a Guide to Cultivation. —From the side of the 
plant itself—aquatic adaptation is so distinctive, so different from 
terrestrial and epiphytic, as to have been always a natural botan¬ 
ical indication of cultural conditions upon which the gardener has 
acted; and if horticulture can derive guidance from such prom¬ 
inent botanical features, appreciation of the significance of plant- 
form in terrestrial and epiphytic plants should be no less in¬ 
structive. 
Water-conservation and Water-obtention. —In the attitude of 
these plants to their water-supply we recognize conservation, 
mainly exhibited in the shoot, and obtention, chiefly centered in 
the root, and these are varyingly correlated, predominance of the 
