An experiment was undertaken to determine the effect of varying amounts of water upon both the gross and the microscopical development of P. communis. 48 dwarf pear trees were divided into 4 lots which were treated uniformly except for watering. Flower clusters were more abundant on trees given more than the minimum amount of water. The number of flowers to each cluster averaged less when abundant water was supplied, due to the high percentage of axillary clusters produced. Abscission of blossoms and partly developed fruits was more pronounced where least water was available. The number of fruits matured by a tree in any one season appeared to have a greater effect on the size of the individual fruits and on the crop produced the following year than did the actual amount of water applied to that tree. With a small crop moderate watering was associated with production of full-sized, normal fruit. With a large crop, moderate watering was associated with production of much smaller and a poorer quality of fruit than when abundant water was applied. A pronounced shortage of water resulted in small fruits of poor flavor and quality. The value of thinning to secure increased size in case of water shortage is emphasized. There appeared to be a close qualitative and quantitative relationship between shoot growth and fruit development, regardless of the amount of water that a tree received. A large fruit crop seemed to make less demand on the water supply than did large shoot growth. The most pronounced difference in gross topography of the tissues is in the extent of the xylem area. As between a large, medium, and small amount of water, this stands in the proportion of 15 to 2 to 1 respectively. The cortex is largest in the moderately watered lot. A comparison of cells showed a number of definite differences in the cortex, phloem, and xylem cells in the different lots, especially as to number and size. The pith cells seemed practically identical in all lots, regardless of the amount of water applied. A great development of xylem may accompany increased water supply to pear trees in rich soil without resulting in succulence, but in a greatly increased volume of firm, sound wood. An attempted interpretation of the results secured suggests that, following changes in the water supply, alteration in the metabolic processes may be due to physical or nutritional causes or both.