1316 



PHOTOGRAPHY 



PHRYNIUM 



coated with a silver chloride rather than a silver bromide 

 emulsion. The slide is usually faced with a paper mask, 

 so as to include only the desired portions of the picture, 

 and protected by a cover glass. Negatives of any size 

 may be used if a suitable arrangement is provided for 

 reduction. This can readily be arranged by an adapta- 

 tion of the camera-stand illustrated in Fig. 1768. A pair 

 of light bars are added, running from the top of the 

 plate-glass frame to a support at the other end of 

 the stand, and a piece of heavy muslin or light canvas 

 thrown over this serves to exclude the excess of light. 

 A ground-glass frame is added back of the plate-glass, 

 which latter is removed to give place to a turn-table 

 arrangement, made to take and hold negatives of vari- 

 ous sizes. In practice, the ground glass end is turned 

 toward the strong light, the negative to be used is ad- 

 justed in the turn-table, and the image focused in the 

 camera as usual. The 5x7 size largely used by hor- 

 ticulturists is in just the right proportion for the 

 ordinary lantern plate of American practice, which is 

 3% x 4 inches. Slides may also be made by contact, if 

 the negative to be used is of suitable size. The familiar 

 4x5, 3% x3% and 3% x 1% hand-camera films are often 

 so used, being placed in contact with a lantern plate in 

 an ordinary printing frame, and given a short exposure 

 to an artificial light. Such slides are seldom of good 

 quality. If it is required to make lantern-slides from 

 diagrams, engravings or any positive material, a nega- 

 tive must be first prepared, for making which the verti- 

 cal position of the camera stand (Fig. 1769) is very 

 convenient. 



In making lantern-slides, it is important to learn the 

 proper exposure, for errors in exposure cannot be cor- 

 rected in development to any great extent. The careful 

 worker will expose several plates upon the same subject, 

 give all the same development, and act upon the ex- 

 perience thus gained. 



The only work treating specifically of the photography 

 of flowers and trees is a previously mentioned mono- 

 graph in The Photo-Miniature, No. 13, published by 

 Tennant & Ward, New York. In the same series of 

 monographs is an excellent treatise on the production 

 of lantern-slides (No. 9), and another on modern lenses 

 (No. 1), previously cited, j. HORACE MCFARLAND. 



PHOTOSYNTHESIS. The term Photosynthesis is 

 derived from Greek words signifying "light" and "put- 

 ting together." It is applied to that process by means 

 of which, under ordinary circumstances, green plants 

 build up organic or carbon - containing compounds. 

 Carbon is the element which as a rule denotes organic 

 substance. It is an essential constituent of the cell 

 wall, or fiber, and of the protoplasm; likewise of starch 

 and of sugar. Green plants manufacture practically all 

 of the organic matter which may eventually furnish 

 food for plants and animals, so that all life is ulti- 

 mately dependent upon them. 



Ordinary air contains only about .04 per cent of car- 

 bon dioxid ; yet the green plant as a rule obtains all of 

 its carbon from the air. Chlorophyll and light are abso- 

 lutely essential in order that organic sub .fcance may be 

 manufactured. Chlorophyll, the substance which gives 

 the green color to leaf and branch, usually occurs in defi- 

 nite plasmic bodies, which are commonly oval in form. 

 These chlorophyll bodies absorb radiant light and thus 

 obtain energy or power to work. This energy cannot be 

 obtained by the common plant in any other way, as by 

 the absorption of radiant heat from a stove. The cell 

 sap absorbs the carbon dioxid which has diffused into 

 the leaf (see Physiology of Plants), and the energy 

 obtained from light works upon the molecules of carbon 

 dioxid (COg) and water (H 2 O) of the cell sap in such 

 a way that these molecules are rearranged and united. 

 A molecule of some simple carbohydrate, perhaps 

 formaldehyde (CH 2 O), is formed; and some of these 

 molecules are perhaps immediately condensed to sugar 

 (C 6 H 12 O 6 ). In this process more oxygen is supplied 

 by the water and carbon dioxid than can enter into the 

 organic product, and this surplus oxygen is thrown off. 

 This whole process is called photosynthesis. 



An accumulation of sugar in the leaf would hinder the 

 further manufacture of this product and much of the 

 sugar formed is, indeed, immediately diffused to other 



cells. The leaf assimilates very rapidly in sunlight, 

 and the surplus sugar formed is changed to starch, an 

 insoluble product. This starch is usually removed from 

 the leaf at night. In some way potassium salts seem to 

 be necessary in the first manufacture of sugar, perhaps 

 aiding in the condensation changes. 



It is probable that no plant containing chlorophyll in 

 genetic connection with its protoplast remains long 

 entirely inactive in assimilation, when illuminated. 

 The red end of the spectrum embraces the colors which 

 are principally concerned in the activity of the chloro- 

 phyll function. Photosynthesis is most rapid under 

 those conditions of temperature and food supply which 

 best stimulate growth. The process is more rapid, how- 

 ever, when the amount of carbon dioxid in the air is 

 slightly increased. The presence of other coloring mat- 

 ters, such as brown and red, in the assimilating organs 

 does not mean that chlorophyll is absent, and that other 

 substances may replace it. Chlorophyll may be present 

 but veiled by a more prominent color. It is improbable 

 that any other coloring matter besides chlorophyll and 

 a related substance, etiolin, is effective in carbon dioxid 

 assimilation. 



Photosynthesis may be inhibited by too intense light, 

 by extremes of temperature, and by deleterious chemical 

 agents. It ceases immediately in darkness, and is very 

 feeble in weak light. 



The results of photosynthetic activity may be noted 

 in this way: An active branch of elodea or other pond 

 weed may be kept in a vessel of water in the dark until 

 it shows no starch with the iodine test. The branch is 

 then placed in spring water, which contains consider- 

 able air. On placing the experiment in sunlight, 

 bubbles of oxygen will immediately be given off. This 

 indicates that photosynthesis is active ; and after a time 

 starch may be found in the leaves. g t M. DUGGAR. 



PHRAGMITES (Greek, growing in hedges, which, 

 however, does not apply to this grass). Graminece. 

 Species 3, one in tropical Asia, one in South America, 

 and one, our species, cosmopolitan. Tall and stout per- 

 ennial reed grasses with long running rootstocks and 

 terminal panicles with aspect of Arundo. Spikelets 

 3-7-fld. Differs from Arundo chiefly in having the low- 

 est fls. staminate, the flowering glume sharp-pointed 

 but not bifid, and the hairs of the spikelet confined to 

 the rachilla. 



communis, Trin. COMMON REED. Culm usually 8-12 ft. 

 high : Ivs. 2 in. wide. Marshes and along edges of ponds. 

 The ornamental feathery drooping panicles appear in 

 late summer or autumn. Gn. 31, p. 33. 



A. S. HITCHCOCK. 



PHRYMA (one of the many names which Linnaeus 

 never explained). Verben&cece. A genus of one species, 

 a hardy, perennial herb of little horticultural value. It 

 has slender branches, coarsely toothed ovate Ivs. and 

 small purplish or rose-colored opposite fls. borne in 

 long, slender terminal spikes. It seems to have been 

 rarely cult, in Europe and is offered by one American 

 dealer in native plants. 



Phryma is an outlying member of the Verbena family, 

 and is by some authors made the sole example of a 

 family of its own. This is because its ovary is 1-celled, 

 while the rest of the Verbenacese, as a rule, have a 2- 

 or 4-celled ovary. There is some evidence for regarding 

 it as a 2-celled verbenaceous plant in which only half of 

 the ovary develops. This plant has the inflorescence of 

 the Verbena tribe and the habit of Priva. Generic char- 

 acters are: ovule solitary, erect, orthotropous, laterally 

 affixed at the base: seed without albumen; cotyledons 

 convolute; radicle superior. 



Leptostachya, Linn. LOPSEED. Height 2-3 ft.: Ivs. 

 3-5 in. long, thin, the lower long-stalked: fls. at first 

 erect, soon spreading and the calyx in fruit closed and 

 abruptly reflexed against the axis of the spike, the teeth 

 long, slender and hooked at the tip. June- Aug. Com- 

 mon in moist and open woods, Canada to Minn., South 

 to Fla. and Kans. B.B. 3:205. 



PHRYNIUM (from Greek word for toad, because the 

 plant inhabits marshes ) . Scitamindcece. About 20 herbs 

 of the Old World tropics with creeping rootstocks and 

 large oblong showy radical leaves. The genus is closely 



