2 iS Bretland Farmer. 
system that is capable under the conditions of its existence of 
causing substances to enter into new chemical and physical combi¬ 
nations. The mechanism itself is vastly complex, but it is thought 
of as owing its properties primarily to the manner in which its 
constituent elements and radicles are grouped together. 
The outcome of its operations—the structural characters that 
will finally appear—depend for their existence on the character of 
the living substance having regard to all the stimuli to which it is at 
the time capable of reacting. 
Thus Kny’s experiments on cuttings planted upside down are 
of interest in this connection, and the old experiment of Sachs on 
the Yucca plant fall into line with them. On these reversed plant 
cuttings roots appear near the apical ends and shoots at the basal 
ones. The same result may be arrived at by pegging down the ends 
of blackberry runners, there root close to the apex, and by 
severing the rooted part of stem from the parent-plant, the buds 
behind the roots may be made to unfold, especially if the more 
apical ones be prevented from growing. 
Now it is obvious in the above mentioned cases that the normal 
relation of the apical protoplasm to gravitation has been interfered 
with, but we can hardly omit to consider gravity as one set of 
stimuli that is known profoundly to influence the mechanism of the 
young formative protoplasm of stems and roots. If therefore we 
disturb this relation, is it to be expected that nutritional stimuli will 
go on producing the same effect as before? Is it not more 
reasonable to think that the alteration in the results of vital activity 
under the new conditions are in a large degree conditioned by 
consequent changes produced in the working of the mechanism 
itself, rather than in the direction of flow of specific organ forming- 
materials? I would refer in this connection to those physiological 
(and dependent morphological) changes that occur in the younger 
lateral shoots and roots when the “leader” or the tap-root may 
happen to be irretrievably injured but is functionally replaced by one 
or more of these lateral members. 
Another remarkable series of phenomena are associated with 
growth. I mean the self-regulation of the structure of a plant as 
a whole. In this self-regulation is also involved the purposeful 
nature of the response to various stimuli. The latter point may be 
passed over for the present, but with the remarks that firstly as a 
matter of fact a large number of characters of any plant do not 
seem explicible on teleological grounds at all, e.g. the forms of many 
