Part 4 (2/2)

In soans are borne directly on the filae zoospores are for 22, _A_), and are produced singly in the ends of branches that becoreen, and filled with very dense protoplasm This end becomes separated by a wall from the rest of the branch, the end opens, and the contents escape as a very large zoospore, covered with numerous short cilia (_A_ ii) After a short period of activity, this loses its cilia, develops a wall, and begins to grow (III, IV) Other species (_B_) produce similar spores, which, however, are not motile, and remain within the mother cell until they are set free by the decay of its wall

ORDER V--_Characeae_

The _Characeae_, or stone-worts, as soreen algae that it is highly probable that they should be separated fro 23), called stone-worts froiving the upon the bottoe in size froht

The plant (Fig 23, _A_) consists of a central jointed axis with circles of leaves at each joint or node The distance between the nodes (internodes) th of several centimetres The leaves are slender, cylindrical structures, and like the stem divided into nodes and internodes, and have at the nodes delicate leaflets

At each joint of the leaf, in fruiting specimens, attached to the inner side, are borne two small, roundish bodies, in the co 23, _A_, _r_) The lower of the two is globular, and bright scarlet in color; the other, more oval and duller

Examined with a lens the main axis presents a striated appearance The whole plant is harsh to the touch and brittle, owing to the liround by fine, colorless hairs, or rootlets

[Illustration: FIG 23--_A_, plant of a stone-wort (_Chara_), one-half natural size _r_, reproductive organs _B_, longitudinal section through the apex _S_, apical cell _x_, nodes _y_, internodes _C_, a young leaf _D_, cross section of an internode

_E_, of a node of a soans seen in optical section _o_, oogoniuroup of fila spernified, showing a spermatozoid in each cell _K_, free speronium (_o_), and antheridium (_An_)

_B_, _H_, 150 _J_, _K_, 300 _I_, 50 _L_, 25]

By itudinal sections with a sharp razor through the top of the plant, and le, nearly he 23, _B_, _S_) This from its position is called the ”apical cell,” and froain into two by a wall parallel to the first Of the two cells thus foroes no further division and forms the central cell of an internode (_y_); the other divides repeatedly, forement of these cells is essentially the same in the leaves and ste several cross-sections of the whole bunch of young leaves near the top of the plant, we shall pretty certainly get soure 23, _E_

As the stee internodal cell (_y_) by the growth of cells fro in theaxial cell A section across the internode shows the large axial cell (_y_) surrounded by the regularly arranged cells of the covering or cortex (Fig 23, _D_)

All the cells contain a layer of protoplasm next the ith numerous oval chloroplasts If the cells are uninjured, they often show a very marked movement of the protoplasm These movements are best seen, however, in for internodal cells are not covered with a cortex In _Chara_ they are round

The growth of the leaves is alrowth is li and pointed (Fig 23, _C_) In so cells, assureen color as the cells approach maturity

The plant multiplies non-sexually by means of special branches that may become detached, but there are no non-sexual spores forans have already been noticed arising in pairs at the joints of the leaves The oogoniuonium (_F_, _O_) consists of a central cell, belohich is a smaller one surrounded by a circle of five others, which do not at first project above the central cell, but later completely envelop it (_G_) Each of these five cells early beco twisted as it elongates, and the central cell later has a small cell cut off fro cell, which in the ripe oogonium (_L_, _O_) is surrounded by five, spirally twisted cells, and crowned by a circle of five srown They separate at the time of fertilization to allow the speronium

The antheridium consists at first of a basal cell and a terlobular, divides into eight nearly sih the centre In each of these eight cells talls are next formed parallel to the outer surface, so that the antheridium (apart froed in three concentric series (_G_, _an_)

These cells, especially the outer ones, develop a great a the antheridium its characteristic color

The diameter of the antheridium now increases rapidly, and the central cells separate, leaving a large space within Of the inner cells, the second series, while not increasing in dia for filale row of cells, in each of which is forht outer cells are nearly triangular in outline, fitting together by deeply indentedcells with the attached filaments upon their inner faces

If a ripe antheridiu a few s in the side of the cells They are er than any we have met with Each is a colorless, spiral thread with about three coils, one end being soranules; the otherand delicate cilia (_K_) To see the cilia it is necessary to kill the sperent

After fertilization the outer cells of the oogoniu after a sufficient period of rest

According to the accounts of Pringshei plant consists at first of a row of elongated cells, upon which a bud is formed that develops into the perfect plant

There are two families of the _Characeae_, the _Chareae_, of which _Chara_ is the type, and the _Nitelleae_, represented by various species of _Nitella_ and _Tolypella_ The second family have the internodes without any cortex--that is, consisting of a single long cell; and the crown at the top of the oogonium is composed of ten cells instead of five They are also destitute of the liards the structure of the plant itself, as well as the reproductive organs, especially the very complex antheridiuroup of plants, either above or below them