60 What is Botany ? 
IV. The Phase of Comparative Anatomy and Morphology. 
Isolated anatomical investigations of the insides of plants of course 
began early and morphology grew up with classification hut it was 
the vitalising theory of evolution which gave a scientific significance 
to the comparative aspect of these studies. Plants were not the 
chaos of a special creation but an orderly if complex phylogenetic 
sequence, to be analysed and, in spite of the imperfection of the 
whole record, to be reconstructed by attention to the minute birth¬ 
marks of insignificant structure. The harvest of the main phyla is 
now mostly reaped and further study seems likely to proceed on the 
principle of diminishing returns. There have been some stirring 
pieces of detective work, as the piecing together of the evolution of 
the seed from fossilised types ; or the discovery that pollen-tube- 
fertilisation still bears the class-marks of alternation of 
generations. 
V. The Phase of Plant Physiology. Stephen Hales, in the 
early eighteenth century, was the first to apply to living things a 
general scientific “ chymio-statical ” outlook, and so laid the found¬ 
ations of several chapters of plant physiology. The rest waited for 
the discovery of protoplasm, the physical basis of life, and the 
realisation that what was known of animal functions could, in 
essentials, be transferred to plants. Combining with all this the 
special botanical studies of photosynthesis and tropisms, Sachs 
put together, in a masterly way, the outlines of a coherent physiology 
of plants in the middle of the nineteenth century. Since then 
physiology has received definite recognition as an indispensable but 
rather detached section of the subject. The first English text-book 
of physiology appearedin 1886 : in general text-books, physiology was 
the smallest of the three traditional main divisions. 
VI. The Phase of Genetics. The twentieth century has seen 
the rise of several new phases of man’s outlook on plants. The 
general study of variation and heredity received such an access of 
vigour from the Mendelian rediscoveries that jt rapidly developed a 
body of genetic principles which no biological science can ignore, 
and is making the phenomena of evolution assume quite a new 
aspect. Apart from the gain in understanding of plants, the power 
that genetics has conferred on the botanist has brought honour to 
the whole science. Millions of years of Nature’s evolution have not 
achieved for us so desirable a wheat as the special creation of 
“ Little Joss.” 
VII. The Phase of Ecology. In a quiet gradual way a new 
