1316 



PHOTOGRAPHY 



verohloride rathi 



and pi-ut'Ti.,1 in- ;, en cr 

 may be u^i-.l if a suiiahi. 

 reducticii. This i/au reaii 

 tion of tile camera-staud 

 of light bars are added, 

 plate-glass frame to a 



aplii 



•^trai'-'l 111 I'lLT. 17IJ8. A pair 

 iililiii,' lr..lii thr top of the 

 .[M.rt at tin- other end of 

 •uvy luusliu or light canvas 

 thrown over tliis serves to exclude the excess of light. 

 A ground ^-la~^ tram.- is added back of the plate-glass, 

 which hitt. r i~ r. irhivcl to give place to a turn-table 

 arrangenieiit. made t.. 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 tin- right jiroportion for the 

 ordiiiarv laiitn-n piate ..f .\inrrican i.ra.'li.-e, which is 

 :;', X 1 "iii.'ii.-s, Sli.l.-s Miav aN Tiia.l.- l.v , tact, if 



so used. I" 111- pi a .11 Ml -A itli a lantern plate in 



an ordinar> i^iniMi i n . a i Ln\-en a short exposure 

 to an artiiirial !:.. - > are seldom of good 



quality. If it i~ i. lun. .1 i.. mak.' 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. 1709) 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 (xreek 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 sulistance may be 

 manufa<-i m. ^L i 'ii 1 .i-.^pl! \ II, tin- -nii-taia-e which gives 

 the grciai .•..■..! '<, ',.,11 ,,i,,| i,,.,,,.-l,. a^,,,i\ , ,.,a-urs in defi- 



These ,-l,|..i..|.M.. I, i„„ii,.- ,,,.,. .ia, raoiaiii 1,-lit and thus 

 obtain eut-rt;> ..i p..rt.r i.. u.nk. 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 (CO2) and water (H2O) of the cell sap in such 

 a way that these molecules are rearranged and united. 

 A molecule of some simple carbohydrate, perhaps 

 formaldehyde (CHoO), is formed; and some of these 

 molecules are perhaps immediately condensed to sugar 

 (CeHiaOe). In this process more oxygen is supplied 

 by the water and carbon dioxid than can enter into the 

 organic product, and this surplus oxvi^'en is thrown off. 

 This whole process is calle.l |ili,,f..sviithr.is. 



An accutnulation of sugar in ih.. 1. .if would hinder the 

 further manufacture of tlii- inMilurt ami much of the 

 sugar formed is, indeed, iniinediately diffused to other 



very rapidly in sunlight, 

 1 is changed to starch, an 

 h is usually removed from 

 ,y potassium salts seem to 

 ifacture of sugar, perhaps 



laiiiiaining chlorophyll in 



entiL'!) iiia..iiv.- in assiniilati.m, when illuminated. 

 The ri il i-nil of tin- siic.tnini iinhrac-es 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- 



ightly 



ters, such as laowu an.l r...l, in ilii. assiniilaiing organs 

 does not mean that .lilor.ij.h) II is aliseiit, 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 photosyntli.ti.- a.tivity may he nof.d 

 in this way: An acti\ ■. la aia-h of ,.|o,i, a ..i- oih,r |iond 

 weed may be kept in a v.ss,.! of « aii r in the ilark until 

 it shows no starch wit 11 tin- io.liiie test. 'I'he hraneh Is 

 then placed in spring water, which contains consider- 

 able air. On placing the experiment iu 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. 3_ m. DnaoAB. 



PHEAGMlTES (Greek, groining 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 Amndo. 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. 



commAniB, Trin. Cosimon Reed. Culm usually 8-12 ft. 

 high: lvs.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. 



FHB'fHA (one of the many names which Linnaeus 

 never explained), t'erbendceie. 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 VerbenaceEP, as a rule, have a 2- 

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

 it as a 2-celled verbenacer.us plant in which only half of 

 the ovary develops. Tliis j.lant has the inflorescence of 

 the Verbena tribe and tin- halht of Priva. Generic char- 

 acters are: ovule solitary, en .t. urthotropous, laterally 

 affixed at the base: seed without albumen; cotyledons 

 convolute; radicle superior. 



LeptOBt&chya, 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 

 toFla. and Kans. B.B. 3:205. 



PHE'tNIUM I from Greek word for toad, because the 



plant inliahits marshes). Scitamindcecf. About 20 herbs 

 of the ( Mil World tropics with creeping rootstocks and 

 large oblong showy radical leaves. The genus is closely 



