LYCOPODIE.E. 



[ 484 ] LYMPHATIC SYSTEM. 



gradually elevated on a thread-like stalk, 

 and separate, displaying two terminal buds 

 between them, whence the first bifurcation 

 of the stem proceeds. 



This mode of reproduction allies the family 

 very closely to the double-spored Marsi- 

 leaceae, and separates them from the Ferns 

 and Equisetaceae, in which the prothallium 

 is ^ formed outside the spores, after the ger- 

 mination of the single and only kind of spore 

 which these plants possess. And by recent 

 authors, the Lycopodiacese are separated 

 from the Selaginaceae, on account of the 

 isosporous fructification of the one, and the 

 heterosporous fructification of the other. 



The order Lycopodiacese is divided into 

 two families, in accordance with the struc- 

 ture of the sporanges : 



Families. 



LYCOPODIE^;. Sporanges simple, one- 

 celled. 



:. Sporanges compound, many- 

 celled. 



BIBL. Hofmeister, Vergl. Unters. 1851, 

 111; De Bary, Ann. Sc. Nat. 4 s<r. ix. 30, 

 Ann. N. H. 3 ser. iii. 189; Faukhauser, 

 Bot. Zeit. 1873; Strasburger, Bot. Zeit. 

 1873 ; Sachs, Bot. 474. See also ISOETES. 



LYCOPODIE'vE. A family of Lycopo- 

 diaceous plants, distinguished by their 

 simple one-celled sporanges. The existing 

 kinds are all herbs, mostly creeping over the 

 ground ; but some of the fossil kinds, met 

 with especially in the Coal-measures, were 

 large trees, the Lepidodendra. Genera : 



Lycopodium. Sporanges all of one kind, 

 containing numerous small spores resem- 

 bling pollen-grains. 



Selaginella. Sporanges of two kinds, the 

 greater part resembling those of Lycopo- 

 dium ; one, situated at the base of the spikes, 

 larger, often four-lobed, and containing only 

 four large spores. 



LYCOPO'DIUM, Linn. A genus of Ly- 

 copodiese. This has been sufficiently cha- 

 racterized under the head of Lycopodiacese. 

 There are more than half-a-dozen British 

 species, mostly alpine plants ; but L. inun- 

 datum occurs on bogs in all parts of Britain. 



BIBL. Hook, Br. Fl.; Babington, Br. 

 Bot. ; Francis, Br. Ferns, 8fc. See also 

 LYCOPODIACEJE. 



LY'GEUM, Linn. A genus of Grami- 

 naceae ; L. spartum is Esparto-grass. 



L YGO 'DIUM, S wart z .A genus of Schi- 

 zaeaceae fPolypodiaceous Ferns), consisting 

 of beautiful climbing plants, with conju- 



gate, palmate, lobed, or pinnate leaves, 

 having the sessile sporanges in double rows 

 on the teeth of the pinnules (fig. 437), each 



Fig. 437. 



Lygodium reticulatum. 

 Portion of a leaf, with fertile pinnules. Nat size. 



having a hood-like special indusium Cfio-s 

 438, 439). 



16 sp. ; tropical. (Hook, Syn. 437.) 



Fig. 438. 



Fig. 439. 



Lygodium reticulatum. 



Fig. 438. Tooth of a pinnule with overlapping indusia. 



Magn. 20 diams. 

 Fig. 439. The same, with the indusia removed to show 



the sporanges. Magn. 20 diams. 



LYMPHATIC SYSTEM. This consists 

 of the lymphatic or absorbent vessels, and 

 the lymphatic glands. 



The lymphatic capillaries commence in 

 the various tissues and organs, as fine net- 

 works or irregular lacunas. The lacunae are 

 connected by canals and clefts, and form a 

 lymph-canalicular system. The lymphatics 

 of the intestines the lacteals, commence as 

 caeca. 



In structure the lymphatics resemble the 

 veins, but the walls are thinner in propor- 

 tion to their calibre; they are also fur- 

 nished with valves, formed by folds of the 

 inner and epithelial coats. 



The lymphatic capillaries are larger than 

 the blood-capillaries. At the surface of the 

 serous membranes, the lymphatics are con- 



