Apeil 1, 1892.] 



KNOWLEDGE. 



63 



in woods or on shaded banks, little plants, in such forms 

 as those shown in Figs. 34, 35, and 86. These show two 





^5 



Figs. 34, 35, 36. — Jungermannia. ar, archegones; 

 «, sporangium. After nature. — A.F. 



species of Jimgermannia — of the family .Jungermanniaceie 

 of my table A. The genus bears a somewhat uncouth 

 name, and one wishes it had a pleasanter one than this, 

 which was bestowed upon it in honour of a worthy German 

 botanist. It has been said that the names of the Mexican 

 kings before the conquest rob them of the fame which 

 their merits deserve ; and so long as these little plants 

 bear this name, I see no hope that they should ever attain 

 popularity. 



That these httle plants have great 

 sp hkeness to ordinary Mosses must be 

 c ,..-■•■■' conceded, but the student who looks 



at them attentively will soon see some- 

 thing diflerent about their general 

 appearance. This is partly due to the 

 pecuhar way in which the leaves are 

 inserted — the lines of attachment of 

 the leaves to the stem generally forming 

 an angle like a V. But other drSer- 

 ences will be apparent from the figures. 

 The sporangium, as in the Mosses, 

 takes its rise from an archegone. In 

 the Mosses this organ is concealed in 

 modified leaves, and is generally speak- 

 ing not easy to detect. In these 

 Jungermanniaceffi the archegones form 

 conspicuous green organs (ar) in which. 

 in the earher stages, the dark-coloured 

 sporangia appear to rest (Fig. 36, s). 

 They are subsequently raised on a 

 seta or stalk, generally of a perfectly 

 ■white cellular structure. The spor- 

 angium is not di-s-ided into capsule 

 and lid, but opens as shown in Fig. 37, 

 by the springing backward of the four 

 leaves which constitute it, and emits 

 large quantities of spores [sp), inter- 

 spersed with very curious structures, 

 known as elaters [el). These elaters, 

 with some attached spores, are seen 

 more highly magnified in Fig. 38. 

 The elaters are endless threads, twisted 

 into spirals, and when liberated the 

 spirals rapidly twist and twirl about, 

 and in so doing, aid in dispersing the 

 spores. The spectacle of an opening 

 sporangium of a Jungermannia is a 

 very interesting one. 

 It is remarkable that in the true Mosses, with their 

 much more highly organized capsules and spore cases, 

 these elaters have disappeared. 



If the patience of my reader hold out, I will ask him, 

 for the last time, to refer back to my table A, where he 

 will find that last of all in the series come the Marchantiaca, 

 so named fi-om the best known species of the group, the 

 MarchantM polymorpha, a plant so remarkable and so 



/ 



iHG. 37.— Part of a 

 Junker man nia, mag- 

 nified ; ar, arche- 

 gone ; se, seta or 

 stalk; cap, capsule of 

 four leaves opening 

 and emitting sp, 

 spores and el, ela- 

 ters. After nature. 

 — A.F. 



Fig. 38. — Spore,* and elaters of Jungennaiinia 

 magnified. ^jB, spores; e/, elaters. After nature 

 — A.F. 



worthy of full consideration, that I fear that if I embarked 

 on it I should weary my reader beyond endm-ance, so I 

 leave it, at least for the present. 



Distribution in -i 



Time. — It win be 

 interesting now 

 to enquii-e how ^P 

 long the present 

 Moss flora of 

 England has 

 existed. How far 

 back can wecarry 

 our knowledge of 

 the existence on 

 the world's sur- 

 face of these deli- 

 cate organisms "? 

 It is evident that 

 they have had but a small chance of leaving evidence of their 

 existence as fossil remains, because whilst the strong, 

 aluiost wiry, vessels of the ferns have a great power of 

 resisting decay and so gettingpreserved, the delicate cellular 

 structure of the Mosses offers Httle or no resistance 

 to that process. Hence it is that the fossil remains 

 of Mosses are not very numerous, or for the most 

 part very ancient. Yet we have some materials to answer 

 the enquiry. Three ancient collections of Mosses enable 

 us to throw some Ught upon it. In an interglacial bed 

 near Crofthead, in Renfrewshire, eleven species of Moss 

 were discovered, and with one possible exception all are 

 well-defined British species of the present day. If we take 

 Mr. Wallace's chronology, and hold that 80,000 years have 

 passed since the Glacial epoch disappeared, and 200,000 

 yeai-3 since the Glacial epoch was at its maximum, we may 

 perhaps give from 100,000 to 150,000 years for the age of 

 this Uttle collection. Out of the eleven Mosses discovered, 

 seven belong to the genus Hypuum, or the famOy 

 Hypnaceae. This collection, then, is evidence, so far as it 

 goes, (1) that the existing Moss flora is as old as the inter- 

 glacial epoch ; (2) that the Hypnaeefe were as dominant 

 then as now; and (3) that the specific forms have remained 

 constant since that epoch. 



Another collection of fourteen Mosses has been dis- 

 covered in a drift in the Clyde valley above the Bovilder 

 drift, and tends to confirm the previous conclusions ; as aU 

 the species are existing, all now inhabit the valley of the 

 Clyde, and the Hypnaces are still predominant," though 

 not in so great a proportion as in the Renfi-ewshire bed. 



A third collection has been found at Hoxne, in Suffolk, 

 in a lacustrine deposit, probably resting in a hollow in the 

 boulder clay. Together with phanerogams of an arctic habit, 

 have been found the remains of ten Mosses, which are 

 described by Mr. Mitten as looking "like a lot of bits 

 drifted down a mountain stream." They are all still 

 dwellers in our island, and exhibit, like the other collec- 

 tions, a preponderance of the family of Hj-pnace*. 



But we can give some evidence of more ancient date. 

 Heer inferred the existence of the Mosses in the Liassic 

 period from the presence of remains of a group of small 

 Coleoptera, the existing members of which now live amongst 

 Mosses — an inference which seems not very strong. But 

 recently the remains of a Moss have been found in the 

 carboniferous strata at Commentry, in France. It appears 

 to be closely allied to the extant Polytrichum, the mDst 

 highly-developed genus of Mosses ; so that we have here 

 a phenomenon like that which occurs in reference to the 

 Equisetacie and Lycopodiaceae, viz., that the earhest fossil 

 species known belong to very highly-developed forms of 

 the group. 



