AX OUTLINE OF PHYTOBIOLOGY. 



seed is what it is mechanically, chiefly because it is the 

 locomotive stage of the plant. 



The seed is, in origin, a fertilized ovule. The flower 

 is itself a structure for securing locomotion, the locomotion 

 of the male to the female and all of its parts and colors 

 and odors, etc., are adaptations to this end. Immediately 

 after the act of fertilization all of the accessory parts,. 

 cah'x, corolla, stamens, st^de and stigma, become useless, 

 and they either wither and drop off, or else the}' may 

 be retained and made of use to help form the various 

 structures, which the seed needs in order to take 

 advantage of moving agencies ; thus any of them njay 

 form wings, plumes, floats, hooks, pulps, etc. In all such 

 cases the seed itself has no disseminating structures of 

 its own — those of the fruit are sufficient. This occurs 

 commonly in few or single-seeded fruits, which are 

 indeliiscent and where the entire structure ripens oris 

 carried off. But in fruits containing many seeds, the- 

 fruit remains on the plant until all seeds are ripe, and 

 each seed has some arrangement for locomotion by itself. 

 From a biological point of view it does not matter 

 in the least from what part the disseminating structures 

 are developed, but from the morphological side it is very 

 important to trace the exact structural origin of each, 

 peculiarity. It is soon apparent that the same biological 

 end may be attained in the most diverse morphological, 

 ways ; a wing may be either bract, calyx, wall of ovary, 

 or outgrowth of the seed coat ; the pulp of a fruit may 

 be bract, receptacle, calyx, ovary, placenta, hairs or 

 seed-coat, and so on. Any available structure whatever 

 may be expected to be utilized for the formation of a 

 useful feature. What it is which determines what 

 particular morphological part shall be employed in any 

 given case, is usually unknown, but there can be no doubt 



