From Jacob Blis (The Story of Mulberry Bend) to last year's Street of the Flower Boxes, the role of flowers in brightening the lives of slum children has been celebrated repeatedly. This one is saved from excessive sentimentality by an understated text and effective illustrations. The busy life on Timothy's block gives a little boy plenty to watch, even an occasional job (helping Mrs. Olivera stack newspapers), but the yellow flower he finds on a walk with grandmother in the park (and which the park man kindly gives him) is something special, ""the most beautiful thing Timothy had ever seen."" His efforts to keep it growing lead to a rapprochement with cranky Mrs. Valdez and the two repair Mrs. Valdez' flower box as its final resting place. Aside from the quote and Mrs. Valdez' recollection of Puerto Rico, there's no comment on the power of a flower--just a resourceful youngster tending a plant. Despite a somewhat arbitrary use of color, the drawings are lifelike and alive. It's a well intentioned picture book that comes off well.