NATURAL FAMILIES. 



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CLASS 15. 



Stamens dicUnious, that is, in a different flower from the pistils. 

 Having followed Jussieu in his leading principles of arrange- 

 ment, we have now arrived at that class of plants which we 

 term imperfect, as the stamens and pistils are no longer united 

 in the same flower. We here find a large family called Cu- 

 curbitacece, from curvus, curved; this contains the genera of 

 the squash, gourd, cucumber, &c. which have Monoecious, and 

 sometimes Dioecious flowers. 



The Amentacea are also found in Jussieu's 15th class. This 

 family has its staminate flowers arranged with scales, in that 

 form of inflorescence, called an ament. The stems of these 

 plants are woody and exogenous ; you will recollect that such 

 stems increase in diameter, by new wood being formed around 

 the old, and that this new wood is formed from the cambium 

 Fig. 101. which flows downwards between the wood 

 and bark : any thing which interrupts the 

 course of this cambium would naturally cause 

 a protuberance in the trunk, at the spot where 

 the obstruction should take place. Fig. 101, 

 shews a portion of the trunk of an oak surround- 

 ed by the twining stem of a wild vine ; the 

 pressure causing an accumulation of cambium, 

 produced the protuberances which appear 

 above the vine. Walking canes are often 

 made of young stems which are thus knotted. 

 The last family in this claes, and the hun- 

 dredth or last order of Jussieu contains the Co- 

 nifera or cone-bearing plants ; their staminate 

 flowers grow in aments, each flower being fur- 

 nished with a scale which performs the office 

 of a calyx in supporting the stamens. 



The pistillate flowers form cones or strobi- 

 lums. To this family belong the cedar (Juni- 

 perus), pine, cypress, &c. ; most of them con. 

 tain a resinous juice, which is valuable in medi- 

 cine. Turpentine is obtained from the pine ; one species of 

 the Juniperus has been supposed to have furnished the incense 

 offered to the heathen deities. 



Class 15th Cucurbitacese Amentaceae Explain Fig. 101 Coniferae. 



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