SECOND DIVISION OF PLANTS. 



201 



Eqiiisetum. 



Tlieir stems, wliicli are simple or branched, are 

 generally hollow, longitudinally striated, and 

 present at intervals knots 

 or enlargements, from "''■ 



which arises heaths 

 which are slit into a num- 

 ber of shreds, and which 

 Beem to be verticillate 

 leaves united together. 

 Sometimes verticillate 

 branches come off from 

 these knots. The fructi- 

 fications fonn terminal 

 spikes. These spikes are 

 composed of thick, pel- 

 tate scales, similar to 

 those which are observed 

 in the male flowers of 

 several conifene, and 

 among others of the yew. 

 At the lower surface of these scales, grow a kind of 

 capsules, disposed in a single row, and opening 

 by a longitudinal slit which looks towards the 

 axis. These capsules are filled with minute 

 granules, which are composed of a globular part, 

 from the base of which arise four long articu- 

 lated filaments, enlarged at their upper part, 

 and spirally rolled around the globular body, 

 which is a true sporule. 



Influenced by the similarity of form which 

 exists between the reproductive organs of the 

 equisetacete and the stamina of some conifera;, 

 Linnaeus named these organs stamina, without 

 pointing out the organs which he considered as 

 pistils. Hedwig, on the other hand, considered 

 each granule as a hermaphrodite flower ; the 

 globular part was the pistil, and the filaments 

 were four stamina, the pollen of which was situ- 

 ated externally. The equisetoe are remarkable 

 for the quantity of silica or flinty earth which 

 they contain. A species of mare's-tail is very 

 common in our marshes, and is sometimes cut 

 for fodder; otherwise this family of plants arfe 

 of no use to man. 



Charace^. The charae are aquatic and sub- 

 mersed plants, found growing in our ditches, whose 

 slender, branched, green, and sometimes translucid 

 stems, bear at intervals verticillate branches, from 

 eight to ten in number. On the branches of the 

 upper verticles are observed a kind of sporangia, 

 or capsules, three, four, or five in number. Each 

 of them is surrounded at its base by two or 

 three bracteas or abortive branches, which Lin- 

 naeus considered as a calyx. They are unilocular, 

 and contain numerous sporules, collected into a 

 single mass, which has been considered as a single 

 seed. These sporangia are formed of two integu- 

 ments, of which the outer is membranous, trans- 

 parent, very thin, and terminated above by five 

 spreading teeth; the inner hard, dry, opaque, 

 and composed of five small narrow valves spir- 



ally twisted. Besides these organs, there ara 

 also observed on the branches sessile and rounded 

 tubercles of a reddish colour. Most authors 

 describe them as stamina. They consist of a 

 reticulated, transparent membrane, fonning a 

 kind of vesicle filled with a mucilaginous fluid, 

 in which are observed articulated filaments of a 

 whitish colour, and others of a larger size filled 

 with a reddish fluid, closed at one of their ex- 

 tremities, and appearing to open at the othei 

 These tubercles, in the progress of vegetation, 

 shrivel, but do not open. 



This family is composed of the single genus 

 Chara. It was established by Vaillant, in 1719. 

 Linnseus at first placed it in the class Crypto- 

 gamia, close to the lichens, but afterwardschanged 

 his mind, and referred it to moncecia monandria 

 of the phanerogamic plants. The charae are re- 

 markable for the quantity of calcareous matter 

 with which some of them are incrusted; but they 

 are useless to man, either as food or medicine. 



CHAP. XXV. 



DIVISION SECOND, MONOCOTVLEDONOUS PLANTS. 



In the previous chapter have been enumerated 

 and described those vegetables which have a 

 simple structure, and no conspicuous reproduc- 

 tive organs or blossoms: we now come to a second 

 division of plants whose structure is more com- 

 plex, and which are furnished with distinct male 

 and female organs that produce true seeds. 



MoNocoTYLEDONOus PLANTS. These are dis- 

 tinguished by the seed being composed of only 

 a single cotyledon; besides this, there are the 

 following distinctions : 



The internal structure of the stem is com- 

 posed of a mass of cellular tissue, in which are 

 scattered bundles of vascular tubes. 



The nerves of the leaves are generally parallel 

 in the monocotyledons, while they are ramified, 

 or branched, in the dicotyledons. 



The perianth is always simple, there beins 

 only a calyx, which sometimes assumes the 

 colours of a corolla. 



The floral organs are generally three, or a 

 multiple of this number, whereas five is the 

 predominating number in dicotyledonous plants. 



In their general aspect, tliese two gi-eat divisions 

 of the vegetable kingdom differ considerably. 

 The grains, grasses, reeds, palms, are in structure 

 and general aspect totally unlike any familiet 

 in the two-lobed division, and are readily dis- 

 tinguished from them. 



There are twenty-seven families or groups o( 

 plants enumerated by botanists under the head 

 of this division, which are as follow : 



Nagadece. Water plants, as the nagvs, zosiera, 

 2c 



