388 IDTOPHTSICS. 



with leafless stems, often growing on rocks ; and fungi, or mush- 

 rooms, and similar plants. 



The genera of plants, are farther distinguished by characters of the 

 flower and fruit ; while the species, are distinguished by the leaves, 

 and other minor differences. In general, plants of the same genus 

 possess similar medical and other properties ; but this rule does not 

 apply to the Linnean classes and orders ; which, as we have before 

 remarked, bring together plants of widely different characters. To 

 remedy this deficiency, is the object of the natural system ; in which 

 plants are arranged in the three classes of dicotyledonous, monoco- 

 tyledonous, and acotyledonous, distinguished by the number of 

 cotyledons found in the seed, which is deemed a predominant 

 characteristic. The farther explanation of this system, we must 

 reserve for the next section ; in order to connect it with references 

 to as many important plants as we have room to mention. 



4. Descriptive Botany, properly includes a description of plants, 

 duly arranged ; by means of which the genus, species, and proper- 

 ties of any given plant may be recognized. We shall here connect 

 it with the natural system ; and commence with the dicotyledonous, 

 or exogenous class of plants : which have stems of bark, wood, and 

 pith ; leaves with branching veins ; the parts of the flower usually 

 with a four fold or five fold division ; and the seeds with two or 

 more cotyledons. This class is divided by Lindley into three sub- 

 classes ; polypetalss, having distinct petals, as the rose, and pink ; 

 monopetalse, having but one petal, forming the corol, as in the cur- 

 rant and potato ; and incomplete, without petals, as the walnut, oak, 

 and buckwheat ; to which other writers have added a fourth sub-class, 

 anomalse, including the achitospermous plants, which have no cover- 

 ing to the seed, as the pine and cedar. 



The polypetalous plants, are divided by Lindley into the albumi- 

 nous group, having the embryo of the seed shorter and smaller than 

 the albumen or mealy part, as in the currant and grape ; the epigy- 

 nose group, having the flower above the ovary or seed vessel, as in 

 the cucumber and melon ; the parietose group, having the placenta 

 to which the seeds are attached, parietal or forming a wall around 

 them, as in the cabbage and violet; the calycose group, having two 

 sepals of the calyx exterior to the others, as in the maple and flax ; 

 the syncarpous group, having the carpels or pods compactly united, 

 as in the hollyhok and pink ; the gynobaseose group, having five 

 carpels or fewer, around an elevated axis, as in the geranium and 

 nasturtion ; and the apocarpous group, having the carpels or pods 

 distinct, as in the rose, apple, peach, pea, and clover. 



The monopetalous plants, comprise the polycarpous group, hav- 

 ing the ovary composed of many carpels, as in the honeysuckle and 

 whortleberry ; the epigynose group, having the flowers above the 

 ovaries, usually with two carpels, as in the cardinal flower and elder ; 

 the aggregose group, having the ovary composed of but one perfect 

 carpel, as in the dandelion, thistle, and daisy; the labiose group, 

 having ovaries of two carpels, within unsymmetrical flowers, as in 

 sage, and mint ; and the dicarpous group, having ovaries with two 

 carpels, within symmetrical flowers, as in the ash, potato, and tobacco. 



