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DI?. M. T. MASTERS OS THE MOKPHOLOGY, 



power there is no escape short of gradual extinction. These 

 latter are adaptive and serve, or have served, some useful pur- 

 pose. Thus the nature of the root depends upon the conditions 

 of the medium in which it grows ; the direction of the branches, 

 and the arrangement, structure, and movements of the leaves are 

 clearly in relation with the varying intensity and changing direc- 

 tion of the light. Other modifications have reference either to 

 the protection or to the dispersal of the pollen or to similar 

 requirements in the case of the embryo and seed. These and 

 like matters are kept in view throughout the following pages. 



The observed changes are, as universally the case, brought 

 about by variations in the intensity of growth and development, 

 as by an arrest, excess, or perversion of growth and by similar 

 conditions of development. Growth is here understood to be mere 

 increase in bulk without attendant differentiation, while develop- 

 ment implies progressive or regressive change — greater or less 

 differentiation. Changes in the one process are often, but not 

 necessarily always, associated with corresponding diversity in 

 the other. Any particular change in one direction is pretty 

 sure to be accompanied by co-relative changes in others. The 

 changes in question may be continuous and uniform or they may 

 be interrupted for a time to be afterwards resumed. These several 

 mutations and rhythmical alternations bring about manifold or 

 pleiomorphic conditions, which in the case of the Coniferae are 

 very remarkable. One such illustration may here be given in 

 the case of the shoots of Finns from the bud-stage to the fully 

 developed state. In the unopened bud w r e have an illustration of 

 arrested growth and development in the case of the bud-scales ; 

 the central axis is also for the time arrested in its growth, the 

 arrest being followed, in response to the stimulus of augmented 

 heat, by rapid elongation, and by the corresponding development 

 of the secondary leaves. In the male inflorescence there is also 

 arrested development manifested in the enveloping bud-scales, 

 followed in due course by the elongation of the axis and the 

 differentiation of the tissues of the leaves into sporophylls or 

 anthers. In the female flower there is similar arrested deve- 



























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lopment in the environing scales, and generally speaking a 



low degree of differentiation in the bracts. These 

 are serially continuous with, and obviously homologous with 

 the leaves. The fruit-scales within the bracts present some 



able illustrations both of arrest and. so to speak, of 













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