LEMNA 



LEMON 



1837 



2131. Floral details 

 of Lemna minor, aa^ 

 stamens ; b, pistil. 

 lEnlarged) 



ponds with a iiumtlo of f;iviMi. 'I'lu' Iciiinas anil .-ipiio- 

 (iolas aro most luieful bccausi' larfjcr anil more con- 

 spicuous than the wolHias. Tlicy arc c;isily gathered 

 for schoolroom and home aquaria, and may be pro- 

 cured from specialists in aijuatics and native plants. 

 Ducks anil .some fish eat these plants. One of the 

 common duckweeds is shown times its natural size 

 in Fip. 2i:iO. The leninas are without any distinct sts., 

 a whole plant commonly consisting of 1 miniature If. 

 and 1 unhranched root which has no vascular tissue. 

 These Ivs. are called fronds by the botanist. The i>lants 

 grow separately, or cohere by their edges in 2's or 3's, 

 and nniltiply by similar fronds, which grow out of the 

 edges of the old ones something like buds. The fls. 

 are minvitc and appear on the edge of the frond. They 

 consist apparently of a ])istil and 2 stamens which are 

 inclosed in a sheath, which botan- 

 ists have determined is u spathe 

 by rea.son of the place where it is 

 borne and by homology with re- 

 lated plants. Botanists now con- 

 sider the 2 stamens as 2 fls. and 

 the pistil a third fl. L. 7>unor is 

 said to flower more frequently than 

 any other northern species. Details 

 of its fl. are shown in Fig. 2131, where 

 there seem to be 4 anthers, but there 

 are only 2, each bearing 2 locules. 

 Duckweeds are perennial plants. 

 In the autumn they fall to the 

 bottom of the ditch or pond, but rise 

 again in the spring, and increase in 

 .size. The allied genus Woiffia con- 

 tains the smallest flowering plants. 

 There are about 10 or a dozen 

 species of duckweeds, widely scattered. L. polyrhiza 

 is now known as Spirodda polyrhiza, but Spirodela 

 is considered by Bentham and Hooker a subgenus of 

 Lemna. The common duckweed occasionally infests 

 the small lily ponds (artificial ones), where it is a pest. 

 The sim])le remedj' is to flush the pond and see that 

 common goldfish or carj) are in sufficient numbers to 

 dear off the remainder. 



\. Veins 7-11: roots several (Spirodela.) 

 S. polyrhiza, Schl. Fronds broadly obovate or 

 orbicular, attaining .3 or 4 lines diam., palmately 

 nerved. Common in U. S. 



AA. Veins 1-5: root solitary. [Lemna.) 



B. Fronds oblong, 6 lines Imtg, 3 lines uridc. 



L. trisulca, Linn. J^ronds thin, narrow and minutely 



toothed at one end, thicker and stalk-like at the other, 



usually with 2 young ones growing from opposite sides 



near the ba.sc. V. 3;2(X). — Common in U. S. 



Bh. Fronds broadly ovate or orbicular, 2 lines long. 



L. minor, Linn. Figs. 2130, 2131. Fronds usually 

 cohering in 3's or 4's, rather thick, not minutely toothed, 

 1-2,' 2 lines long. V. 3:2CH). 



Other species of Lemna are native in N. Amer. Of Woiffia there 

 are also a few speees and of Wolffiella one. The wolffias are 

 seldom collected for lawn ponds. WiLHELM MlLLER. 



LEMON (Citrus Li?nonia). Prior to 1894, the culture 

 of the lemon in Florida was an industry of considerable 

 importance. An annual output of 140,000 boxes hiul 

 been reached, but the cold of 1894-l.S9r) injured the 

 trees and marked the beginning of the end of commer- 

 cial lemcm-production in the state for the time at least. 

 Another contributing cause to the extinction of the 

 industry was the development of anthracnose, a fungous 

 disea.se causing brown spots on the fruit, jiarticularly 

 during curing and after shipment. The nature and con- 

 trol of this di.sea.se Wiis not then understood. By 1901- 

 1902 the irop had fallen to only a little over 1,000 boxes. 



Since 1894, the citrous industry of Florida has 



moved southward. In consequence, regions have been 

 opened up, which because of their more favorable 

 location are very free from the blighting effects of cold. 

 There is now a very noticeable awakening of interest 

 in lemon-culture and it would not be surprising if the 

 next ten to twenty years wt)ulil see the industry once 

 more established in the state. The outlook is further 

 improved by the great advancement made in methods 

 of orchard-heating and the control of the disease above 

 mentioned. 



Great care must needs be exercised in the selection 

 of locations for growing lemons. The trees respond 

 readily to increased temperatures and hence are too 

 often in poor condition to withstand the low tempera- 

 tures which often follow. Particular attention must be 

 given to air-drainage and water-protection. Plantings 

 of some size have been made in the last two or three 

 years and still larger ones are contemplated. 



The favorite variety and practically the only one 

 planted is Villa Franca. It has proved to be materially 

 hardier than other varieties such as Genoa and Eureka. 

 The Rough lemon, a variety of uncertain relationship, 

 grows as a wild or semi-wild tree in southern parts of 

 Florida. Occasionally the fruit finds its way into the 

 markets of the state. Its principal use is to furnish 

 seed to grow seedlings on which to propagate different 

 citrous fruits. Everbearing is grown here and there as 

 a home fruit. Ponderosa, a large-fruited variety, is 

 grown as a yard tree. When filled with fruit, the tree 

 is very ornamental and the fruit is valuable for home 

 use. This great fruit may be mistaken for a grapefruit 

 (.see Pomelo). 



Lemon trees in Florida, are grown almost entirely 

 on Sour orange and Rough lemon stocks, choice 

 between the.se two being governed by the soil type and 

 moisture conditions. It is best that the stocks be 

 budded some distance above the ground. In northern 

 Florida, Villa Franca is sometimes grown on Poncirus 

 Irifoiiata stock and fruit is often secured. 



Plantings are usually spaced 20 to 25 feet apart each 

 way and the general care and cultivation is much the 

 same ;is for other citrous fruits. In general, the plan 

 pursued is to cultivate frequently during the usually 

 drj- spring season, March to June, after which a cover- 

 crop of beggarweed, native grasses or cowpeas is given 

 possession of the ground. By the middle of November, 

 this cover-crop should be incorporated with the soil, 

 either by shallow plowing or by cutting it in with a 

 disc-harrow. It has been frequently demonstrated that 

 injury to trees from cold is much less severe if all 

 vegetation is cut into the soil, than if the ground is 

 covered with gr;iss and weeds. 



Pruning requires careful attention to keep the trees 

 low and compact. Lemons are very prone to produce 

 long bare branches without fruiting twigs. They must 

 be headed in to cause the development of fruiting sjjurs 

 well in toward the center of the tree. 



Protection of the fruit and trees must be provided. 

 Up to this time the Schi-ii oil-heater is the best heating 

 device that has been brought forward for this work. 

 The temi)erature must not be allowed to go below 29° 

 F. for any length of time if there is fruit on the trees. 

 With these heaters there is no question but that the 

 trees can be protected against cold in the southern 

 parts of the state. H. Harold Hume. 



The lemon in California. 



In general, the culture of lemons in California is 

 similar to that of oranges f which see). Especially is 

 this true in regard to soil requirements, propagation, 

 irrigation, fertilization, and the like. The picking and 

 handling of the fruit and pruning of the trees, however, 

 difTer radically from that of the orange. 



The commercial lemon areas of California are situa- 

 ted near the coast, chiefly in the counties of San Diego, 

 Orange, Los Angeles, V'entura and Santa Barbara, 



