198 Science of Plant Life 



and in supplying the seeds with the store of nourishment 

 needed for germination and for the early growth of the seed- 

 lings. The reproductive phase of the plant's life is essentially 

 a food-transferring and food-consuming one ; it begins with 

 the production of the flower and ends with the maturing of 

 the seeds. In perennials these phases are not distinct as they 

 are in annuals and biennials. 



The flower. The flower is a specialized shoot, whose end 

 is the production of seed. Commonly the word " flower " 

 is associated with the brightly colored parts that make many 

 of our garden and house plants so attractive. But here we 

 shall include under the term the simple structures associated 

 with seed production in plants like the grasses, poplars, and 

 birches, that have merely scalelike leaves and bracts inclosing 

 the reproductive parts. In the conifers the seeds are pro- 

 duced on scale leaves arranged spirally in cones. These cones 

 may be looked upon as a lower type of flower, structurally 

 very different from the flowers of the monocots and dicots. 



Flower clusters. The arrangements of flowers on stems 

 are so varied in different plants that it is quite beyond the 

 scope of this book to describe the many kinds of flower clus- 

 ters. In many plants the flowers occur singly at the ends of 

 stems or lateral branches, as in the tulip and in some varieties 

 of roses. In other plants they are arranged in groups, as in 

 the spike of the common plantain and cat-tail ; the calkin of 

 the willow, alder, and oak ; the umbel of the carrot, onion, 

 and milkweed ; the raceme of the snapdragon, spring beauty, 

 black locust, and larkspur ; and the composite head of the 

 sunflower and chrysanthemum. The head of wheat and the 

 ear and tassel of corn are other forms of flower clusters. Plants 

 like the yucca, curly dock, rhubarb, broom corn, and hy- 



