510 
The Seed and its Germination. 
indeed the nutrition of the plant, is not yet understood at 
all completely. The efforts which have been made to trace 
the formation of protoplasm, or even of proteid, from the 
simple forms absorbed, have been neither so complete nor so 
successful. Certain advances, however, have been made. The 
tissues of the young plant show, on careful examination, the 
progress of- various forms of matter towards the seat of active 
growth. Growth, or rather the formation of new matter, is in 
plants very largely localised in particular regions. The apex 
of a root or of a shoot is such a part ; a particular region in some 
stems, known as the cambium layer, where are formed the new 
cells which increase the diameter of such stem, is again the 
seat of this construction. Towards these regions, particularly 
towards apical growing points, both sugar, vegetable acids, and 
asparagin, with other allied amide bodies, can be proved to travel. 
But at the growing points themselves no sugar and no amide 
can be detected. There, in the growing cells, the secret of the 
construction of living substance is hidden. A certain amount 
of light, though really very little, has been thrown upon the 
formation of that curious material we have called proteid by the 
study of these parts when furnished with one or more of these 
travelling supplies. When lupins are grown from seeds in 
darkness their tissues are found to be charged with asparagin. 
Their growth only proceeds for a time. If now they are removed 
into the light, and supplied with air, the asparagin disappears, 
and their bulk again begins to increase. It has been inferred 
from this that the construction of proteid demands the presence 
of carbohydrate, such as sugar, and an amide body, such as 
asparagin. When these are supplied to a living cell, and at 
the same time traces of sulphur, and perhaps phosphorus, are 
present there as well, proteid is constructed under the influence 
of the living substance of that cell. From the proteid so formed 
the living substance itself is built up by processes* as yet un- 
known. The cessation of growth in the darkness is due to the 
non-supply of the carbohydrate, as the plant can only form this 
in the light. From the living substance itself we have the 
formation of the other bodies found in cells — cell-wall, or 
cellulose, being always secreted from it. Starch also has been 
found to need the intervention of protoplasm before it can make 
its appearance. 
Though the constructive side of the growth of the- young 
plant thus leaves much to be inferred, the process of germina- 
tion is now to a large extent understood, a very great advance 
in our knowledge having been made in recent years. So fai 
from the process involving nothing more than the transformatior 
