MARCHANTIE.E. 



[ 491 ] 



MARSILEACE.E. 



these circumstances it produces gemma, 

 consisting of little, compressed, oblong 

 masses of cells, of green colour, capable of 

 reproducing the plant. These are found, 

 when mature, in elegant cup-like struc- 

 tures, with toothed borders, sessile on the 

 upper face of the frond (figs. 446, 450). 

 The cup seems to be formed by a develop- 

 ment of the superior epidermis, which is 

 raised up and finally bursts and spreads 

 out, laying bare the gemmse, produced from 

 the internal parenchyma. The gemmae 

 consist at first of a single cell, which di- 

 vides so as to present an upper and a lower 

 (stalk-) cell ; the upper multiplies until it 

 becomes a cellular mass (fig. 451). The 



Fig. 451. 



Marehantia polymorpha. 



A vertical section of the same, with nascent gemmae. 

 Magnified 50 diameters. 



development of this structure presents much 

 analogy to that of the sori of the Ferns with 

 their iudusia and sporanges. 



The Marehantia also increase by innova- 

 tions, or lobes of the frond becoming de- 

 tached from those on which they originate. 



These plants form most interesting ob- 

 jects of microscopic investigation, in all 

 parts of their structure. 



BIBL. Hook. Br. Fl. ii. pt. 1. 105 ; Engl 

 Bot. pi. 110; Mirbel, Mem. Acad. Paris, 

 xiii. 337, 375 ; Nageli, Linncea, xvi. 1842 ; 

 Henfrey, Dev. of Spores fyc., Linn. Tr. xx. 

 103, pi. 11 j Thuret, Antheridtes, Ann. Sc. 

 Nat. 3 ser. xvi. 72, pi. 12 ; Gottsche, Bot. 

 Zeit. 1858, Suppl. ; Strassburger, Jahr. iviss. 

 Bot. vii. 409 ; Sachs, Bot. 354. 



MARCHANTTEyE A family of Liver- 

 worts or Hepaticse. Brit. Genera : Mar- 

 ehantia, Fegatella, Rebouillia, Lunularia. 

 See HEPATICJE. 



MARGAEIC ACID and MARGARINE. 

 The former general ingredient of the fatty 

 matters of both the animal and vegetable 

 kingdom, when crystallized from hot alco- 

 hol, forms minute needles, either isolated 



or in groups (PI. 11. fig. 16 a). The crys- 

 tals differ from those of stearic acid, which 

 form lanceolate single or aggregated plates 

 (PL 11. fig. 16). 



Margarine crystallizes from a hot alcoholic 

 solution in fine needles, mostly grouped or 

 branched, sometimes surrounding globules 

 of oleine, or formino; bulb-like aggregations 

 of needles (PL 11. tig. 15). It is sometimes 

 found crystallized within the cells of fatty 

 tissue (PL 11. fig. 15 a). 



Margaric acid is now regarded as a mix- 

 ture of palmitic and stearic acids, and 

 margarine as a combination of these acida 

 with glycerine. 



BIBL. That of CHEMISTRY. 



MARGIN ULI'N A, D'Orb. A Nodosa- 

 rine Foraminifer, elongate, equilateral, 

 curved or spiral in its earlier portion; 

 chambers globular or compressed ; orifice 

 rounded, marginal. Nodosaria raphanus 

 becomes Marginuline with an eccentric 

 aperture (PL 23. figs. 30-32); and, by gradual 

 modifications, Marginulina passes into Cris- 

 tellaria, with which Williamson unites it. 



Common in existing seas ; and fossil from 

 the Trias upwards. 



BIBL. Williamson, Rec. Foram. 30 ; Mor- 

 ris, Br. Foss. 37 ; Parker & Jones, Ann. 

 N. H. 3. xii. 432; Carpenter, Intr. For. 

 163. 



MARSIL'EA, L. A genus of Marsilea- 

 ceaB (Flowerless Plants), growing in mud, 

 by a creeping rhizome, from which arise 

 erect filiform leaf-stalks, supporting a com- 

 pound four-lobed blade ; at the bases of the 

 leaf-stalks arise also stalked capsules, cham- 

 bered in the interior, being divided by one 

 perpendicular and many horizontal septa; 

 in these chambers are found sacs (sporanges) 

 containing the spores. This plant agrees in 

 all essential respects with PILULABIA. See 

 MARSILEACE^;. 



MARSILEA'CE^E. Afamily of Flower- 

 less plants possessing a slight leafy stem ; 

 composed of a small number of plants, of 

 minute dimensions, but of great interest in 

 a physiological point of view. They are all 

 aquatics, some growing in the mud in and 

 around ponds, others floating on the surface 

 of stagnant waters. They all bear distinct 

 spore-fruits or sporocarps, seated on a stalk 

 arising from the stem. These contain spo- 

 ranges or spore-sacs, differently arranged in 

 the different genera, but agreeing in this 

 respect, that they contain spores of two 

 kinds, macrospores and microsporus, analo- 



