MARCHANTIA. 



[ 414 ] 



MARGARIC ACID. 



It has been mentioned that M. polymorpha 

 does not fruit freely in the shade. Under 

 these circumstances it produces gemmcB, con- 

 sisting of httle, compressed, oblong masses 

 of cells, of green colour, capable of repro- 

 ducing the plant. These are found, when 

 mature, in elegant cup-like structures, with 

 toothed borders, sessile on the upper face of 

 the frond (figs. 450, 454). The cup seems to 



Fig. 454. 



^^6^:^-^^- 



Marchantia polymorpha. 



A collection of gemrase in their involucre. 



Magnified 25 diameters. 



be formed by a development of the superior 

 epidermis, which is raised up and finally 

 bursts and spreads out, laying bare the gem- 

 mae, produced from the internal parenchyma. 

 The gemmse consist at first of a single cell, 

 which divides so as to present an upper and 

 a lower (stalk) cell; the upper multiplies 

 until it becomes a cellular mass (fig. 455). 



Fig. 455. 



Marchantia polymorpha. 

 A vertical section of the same, with nascent gemmae. 



Magnified 50 diameters. 



The development of this structure presents 

 much analogy to that of the sori of the Ferns 

 with their indusia and sporanges. 



The MarchanticB also increase by innova- 

 tions, or lobes of the frond becoming de- 

 tached from those on which they originate. 



These plants form most interesting objects 



of microscopic investigation, in all parts of 

 their structure. 



BiBL. Hook. Brit. Flor. ii. pt. 1. p. 105, 

 Engl. Botany, pi. 110; Mirbel, Rech. anat. 

 etphysiol. sur le Marchantia, Memoires Acad. 

 Roy. Paris, xiii. pp. 337.375; Nageli, FFwr- 

 zel-haare du Marchantia, Linncea, xvi. 1842 ; 

 Henfrey, Dev. of Spores and Elaters of 

 Marchantia, hinn. Trans, xx. p. 103. pi. 11; 

 Thuret, Rech. sur les Antheridies, Ann. des 

 So. nat. 3 ser. xvi. p. 72. pi. 12. figs. 1-5. 



MARCHANTIACEiE.— A tribe of Liver- 

 worts or Hepaticacese, having broadish lobed 

 thalloid fronds, from the bifurcations of 

 which arise stems bearing variously arranged 

 sporanges containing spores mingled with 

 elaters, but destitute of a columella. 



British Genera, 



I. Marchantia. The fructiferous head of 

 the axis radiating. Perichsetes having from 

 one to six archegonia, alternating with the 

 rays of the fruit-head. Perigone 4-5-lobed. 

 Epigone persistent. Sporange bursting with 

 teeth, which are at length revolute. 



II. Fegatella. Fructiferous head scarcely 

 thickened, umbonate. Perichaete absent. 

 Perigones tubular, obliquely split at the apex, 

 connate with each other and confused with 

 the axis. Epigone persistent. Sporange 

 bursting with 5 or 8 teeth, at length revo- 

 lute. 



III. Rehouillia. Fructiferous head conical, 

 somewhat 5-lobed. Perichsete wanting. 

 Perigones bursting by a longitudinal slit, 

 distinct, adnate to the axis. Epigone per- 

 sistent. Sporange bursting irregularly at 

 the apex. 



Nearly allied to these are several interest- 

 ing foreign genera, noticed under Hepati- 

 CACE^, Grimaldia (figs. 336, 337), Fim- 

 briaria{^gs. 338, 339), Lunularia (figs. 333- 

 335). 



MARGARIC ACID and MARGARINE. 

 — The former general ingredient of the fatty 

 matters of both the animal and vegetable 

 kingdom, when crystallized from hot alcohol, 

 forms minute needles, either isolated or in 

 groups (PI. 7- fig- 16 a). The crystals diff*er 

 from those of stearic acid, which form lan- 

 ceolate, single or aggregated plates (PI. 7- 

 fig. \6b). 



Margarine crystallizes from a hot alcoholic 

 solution in fine needles, mostly grouped or 

 branched, sometimes surrounding globules 

 of oleine, or forming bulb-like aggregations 

 of needles (PL 7- fig- 15). It is sometimes 



