The Mechanical Structure of Tlants. 117 



that position it is impenetrable by rain or moisture. When the head has acquired 

 its size and is ready to open, the stalk erects itself for the purpose of presenting the 

 flower and the instruments of fertilization to the genial influence of the sun's rays. 

 This is a curious property provided for in the constitution of the plant ; for if the 

 stem be only bent by the weight of the head, how comes it to straighten itself when 

 it is the heaviest ? These instances show the attention of nature to this principal object, 

 viz. : the safety and maturation of the parts upon which the seed depends. In trees, 

 especially in those which are natives of colder climates, this point is taken up earlier. 

 Many trees produce the embryo of their leaves and flowers in one year, and mature 

 them the following year. There is a winter also to be got over. Now, what we are 

 to remark is, how nature has prepared for the trials and severities of that season. 

 These tender embryos are wrapped up with a compactness no art can imitate, in 

 which state they compose what we call the bud. The bud itself is inclosed in scales, 

 the remains of past leaves or the rudiments of future ones. 



In the coldest climates a third preservative is added, by the bud having a coat of 

 gum or resin, which, being congealed, resists moisture and. frosts. On the approach 

 of warm weather this gum is softened, and ceases to be a hindrance to the expansion 

 of the leaves and flowers. The leaves themselves are packed in capsules or in vessels 

 composed of coats, which, compared with the rest of the flower, are strong and tough. 

 From this vessel projects a tube through which the fertilizing properties that issue 

 from it are admitted into the seed. 



Here occurs a mechanical variety accommodated to the diff"erent circumstances 

 under which the same purpose is to be accomplished. In flowers which are erect, 

 the pistils are shorter than the stamina, and the pollen shed from the anthera into 

 the cup of the flowers is caught, in its descent, on the head of the pistils called 

 stigma. In flowers that hang down or suspended (the crown imperial, etc.), this 

 arrangement is reversed, the pistils being usually the longest, and its protruding sum- 

 mit receives the pollen as it falls to the ground. 



The seed vessels are of an incalculable variety of forms in difi'erent plants, all evi- 

 dently c(?nducing to the same end, namely, the security of the seed. Of the gourd, 

 melon, etc., the seed vessels assume an immense bulk; in stone fruits and nuts, in- 

 cased in a strong shell, the shell itself incased in a pulp or husk ; in numerous kinds 

 of berries, in grapes, oranges, etc., the seed is inclosed in a glutinous syrup contained 

 in a skin or bladder ; in apples, pears, etc., imbedded in the heart of a firm, fleshy 

 substance ; or, as in strawberries, pricked into the surface of a soft pulp. These, 

 and many other varieties exist in what we call fruits. In grain, in grasses, trees, 

 shrubs and flowers the variety of seed vessels is incomputable. We have the seeds, 

 as in the pea tribe, regularly disposed in parchment pods, which, though soft and 

 membranous, are impervious to water ; at other times, as in the bean, lined with a 

 fine down. We have seeds packed in wool, as in the cottonwood, lodged between 

 hard and compact scales; as in pine cones, protected by spines; as in the thistle, 

 placed under a pent-house ; as in the mushroom, in ferns, in slits on the back of the 

 leaves ; or as in grains and grasses covered by strong, close tunicles attached to a 

 stem, according to an order appropriated to each species of plant. 



[CONCLUDED XEXT MONTH.] 



