Ch. II] CHARACTERISTICS OF PLANTS 9 



While typical plants all have the same organs, they are 

 not all alike, but differ greatly in habits, aspect, and details 

 of structure. Some are trees, tall, long-lived, and single- 

 trunked, forming the canopy of forests. Others are shrubs, 

 shorter and less lasting, branching from the ground, and 

 forming the typical undergrowth. Others are herbs, smallest 

 and shortest-lived of all, soft-bodied and mostly green 

 throughout, forming the carpet vegetation of the earth. 

 Then there are plants which grow supported upon others, 

 the climbers and epiphytes : and the plants of strange 

 aspect found in the deserts: and the water-plants, in- 

 cluding the seaweeds : and all of the great number of the 

 small and simple parasites, which occur everywhere amongst 

 other plants. Some kinds possess organs other than those 

 we have mentioned, such as tendrils, pitchers, and 

 tubers, always associated with special habits ; but these parts 

 prove on comparative study to be mostly transformed leaves, 

 stems, or roots, though not all special structures have this origin. 



The organs develop in the individual plants in definite 

 predetermined cycles. Every plant normally originates in 

 a fertilized egg cell, as does the animal in an egg. The 

 egg cell, lying within the ovule inside the flower, is a 

 microscopic protoplasmic sphere, at first without organs; 

 but in the course of development it forms a stem and a few 

 leaves, in which stage it is an embryo within a seed inside a 

 fruit. When, after dissemination, the seed germinates, the 

 embryo develops a root, and more stem and leaves, becom- 

 ing a seedling, and with further repetition of those parts, 

 ultimately an adult plant. Then it begins reproduction 

 by developing flowers, in which sexual cells, egg cells 

 and sperm cells, are formed and brought together, making 

 new fertilized egg cells, thus closing the cycle, which is re- 

 peated in perfect regularity, generation after generation. 



Plants are not, however, merely aggregates of parts per- 

 forming present functions, but include many relics of their 



