Page:The New International Encyclopædia 1st ed. v. 04.djvu/776

* CHLOROPHYCEiE. 678 CHLOROPLAST. an immense numl>er of species. Above the uni- cellular green algse are found filamentous types, sometimes culled confervas, and also membra- nous growths especially well illustrated in the sea-lettuces. Some of the filamentous forms are slimy, iind appear as frothy scums on tlie surface of the water ('pond-scums'). Other kinds, as the genus Vaucheria, form coarse, rough mats at the bottom of ponds and ditches, or on moist earth. The water-net (Bydrodicti/uii) sometimes grows so luxuriantly as almost to fill the water. The highest groups in complexity of body are the stoneworts and certain marine foniis, e.g. Caulerpa, which are differentiated into stems, leaves, and root-like organs of at- CHLOHOPHYCEJi. Desmlds: a, Closterium; h, Micrasterias: c, J, Coemarium. tachnient. The resting stages of some Chloro- phyce» are very conspicuous. The color of 'red snow' is due to the presence of the resting spores of one of the Volvocales. Generally speaking, the algal flora of a pond or ditch depends largely on the season of the year, the chemical nature of the water, and the illumination, but also to a great extent upon biological factors involved in the sjiecial adaptation of species to one another and their environment. There are many special monographs covering various orders in this large group. For general treatment, consult I^ngler and Prantl, Die natiir- lichen Pflanzenfamiiien (Berlin, 18!)9 et seq.). See Ai.cK. CHLOB'OPHYLIi (Neo-Lat. chlorophyllum, from Cxk.X''-"l>^C,chlOros, greenish-yellow -|- pi'/l- hii', plii/lloii, leaf). The grwn coloring matter of ordinary foliage. This is not a single pigment, but a mixture of at least two, one a green jiig- ment, to which the name is sometimes restricted, and a yellow pigment, carotin (q.v. ) or xantho- phyll. Chlorophyll is also often associated with blue (phvcocyanin), browTi ( phycophtein ) , or red (phycoeryjhrin) pigments, especially in the alga; showing these tints. Chlorophyll is only found associated with protoplasm, by which, indeed, it is produced. In some of the small plants it may color the whole protoplasm of the cell, but us>i- ally it is restricted to certain definite portions of the protoplasm called chloroplasts (q.v,). It is restricted to plants, though it is not found in all, being wanting in the wliole class of fungi, and in some of the seed-plants, especially those which live as parasites or saprophytes (q.v.). Chloroplasts have been said to occur in animals, but they turn out on examitialion to be minute green alga-, which live associated with the ani- mal (e.g. hydra, sponges, certain radiolaria, etc.). The amount of chlorophyll in leaves, according to Tschireh, varies from 0.2 to 1 gram per square meter of surface. From the chloroplasts it may be extracted by various solvents, alcohol, ether, fatty and volatile oils, etc., but probably at once undergoes an alteration in its composi- tion. In alcoholic solution it exhibits the ])rop- crty of fluorescence, being emerald-green by trans- mitted light and deep blood-red by reflected light. Molisch's test for chlorophyll is as follows: If a bit of dry tissue to be tested be wetted with a saturated watery solution of potassium hydrate, it instantly turns brown, and after 1,5-30 minutes becomes again green. This change appears imme- diately on heating or adding water. The chemical nature of chlorophyll is not satis- factorily known. It is a complex ami exceedingly unstable nitrogenous carbon compound, probably not containing iron, as once believed. Attempts to analyze it result in so complex a series of de- composition products that it is difficult to draw any certain conclusions. All efforts to purify it or to crystallize it meet with the same difliculty, and all the so-c'alled 'pure chlorophyll' is one or another decomposition product. Chlorophyll is chemically related to hiemoglobin, the red color- ing matter of the blood, as shown by the fact that phyllo])or)5hyrin, a decomposition product of chlorophyll, is vei-y nearly identical with hiemato- porphyrin, a decomposition product of haemo- globin. The coloring matters in a live leaf absorb cer- tain wave-lengths of light, notably /I 680-660 (between the B and C lines of the spectrum). There are also weaker absorption bands about X 01.5-600, ?. .500-.540, A r)30-5i7 (nearly K line), and extensive absorption beyond X 4',)0. These absorbed portions are utilized in part for the making of food (see Photosynthesis) ; though the greater portion of the energy is dissipated in evaporating water. In the absence of chlorophyll, however, no formation of carbohydrate foods can occur. To this there are only unimportant exceptions. Chlorophyll is formed usually only in the plas- tids which lie near the surface of a plant exposed to light of certain intensity. It is produced in darkness in certain exceptional plants, e.g. em- bryos of pines. It is only procraturc and in the presence of oxygen. Probably under the normal conditions of life it is being continually formed and as con- tinually destroyed. Intense light iironiotes its destruction, so that plants may become blanched thereby. Ordinary blanching (e.g. of celery) is accomplished by darkening, whereby the forma- tion of chloroi)hyll is checked. drLOIlOPLAST (from Gk. x^'-'P^':, chlOros, greenish-yellow + 77/aa-(if, plasto.i, formed from TTAaaaew, iihissein, to shape). In botany, the protoplasmic body found in green plants and dis- tinguished by the green pigment chlorophyll. Chloroplasts are developed only in the cells to which a sufficient amoint of light penetrates; therefore, in the larger plants they arc found only in the cells near the surface. The absorp-