THE FARMER'S MAGAZINE. 



103 



KENNINGTON AGRICULTURAL AND CHEMICAL COLLEGE. 



LECTURES ON THE GENERAL PHENOMENA OF THE EARTH, HAVING REFERENCE TO THE 

 PRODUCTION AND MAINTENANCE OF ORGANIC LIFE. 



BY CHARLES JOHNSON, ESQ., PROFESSOR OF BOTANY GUY'S HOSPITAL. 



No. XII. 



In our last lecture we have discussed some of the phy- 

 sical relations between vegetables and animals, and the 

 uncertainties under which we labour in the examination of 

 the lower grades of both. We will now direct our atten- 

 tion to those forms of the first that are capable of being 

 unequivocally regarded as such, examine their structure, 

 and note whatever other circumstances, attaching to their 

 history, may appear likely to assist our endeavours to ob- 

 tain a knowledge of their value in the general system of 

 Nature. 



The adjective term " mineral" is applied, properly, to all 

 modifications of substance which are not organic ; but, as 

 already noticed, certain combinations of matter are never 

 met with except as associated with animal or vegetable 

 life ; while many of the forms of that life require, for 

 their production and maintenance, such an assemblage of 

 elements as can only be brought together by the agency 

 and pre-existence of others belonging to the same class 

 with themselves, to a higher, or (primarily) to a succession 

 of many of a subordinate character. All the operations of 

 organic existence, its alternate production and decay, tend 

 to the fulfilment of this circumstance ;■ and the preparatory 

 process is assigned — upon the land, at least — to the lower 

 and less conspicuous forms of vegetation. 



Botanists, amid their varied and often complicated 

 systems of classification, can never lose sight of certain 

 grand natural assemblages, or rather types, of vegetable 

 organization, which, regarded on a broad scale, may be 

 reduced to nine essentially-marked terrestrial forms — viz. : 

 1, lichens; 2, mosses ; 3, ferns ; 4, grasses; 5, palms and 

 lilies ; 6, firs ; 7, trees and herbs ; 8, parasites ; 0, funguses. 

 The limits of these groups are not in all cases strictly de- 

 finable ; and certain smaller ones occur which do not well 

 associate with either, partaking of the characters of two 

 or more, and thus apparently constituting links of con- 

 nexion between them : but, setting these aside, their gene- 

 ralities are too obvious to be overlooked by any but the 

 most careless observer. The succession of the several 

 groups, as here recorded, is, structurally considered, 

 correct ; the order of their appearance in Nature, perhaps, 

 only partly so : still, in the common course of sequence, 

 the lichen is succeeded by the moss, the moss by the fern, 

 while the grasses and other flowering plants follow ; and, 

 as disease and death overtake these latter, the parasite 

 and the fungus fasten upon them, and hasten their disso- 

 lution. 



Whatever may have been the circumstances under which 

 vegetation commenced upon the earth's surface, the suc- 

 cessional process is that which now prevails. We may see 

 it in action, slowly but surely, in every spot that man has 

 not brought under his own immediate dominion, or obvious 

 causes rendered desolate. Nature is there at work, with 

 unceasing labour, to maintain the necessary supplies of 



nutriment for her vegetable offspring. Some small number 

 of species only, among the higher orders of plants, have a 

 constitution fitted for flourishing upon the loose and shifting 

 sand, or to dwell rooted in the crevices of the hard and 

 insoluble rock ; but even these are not exceptions to that 

 universal law on which the existence of all the visible 

 forms of organic being is now dependent. They live and 

 fatten on the wrecks of others, that have themselves lived 

 and fattened on the i-elics of an earlier and long-extinguished 

 race that drew its nourishment from those of others yet 

 beyond it in the course of time ; and this has been the 

 currency of matter, from a period which man in vain 

 attempts to trace to a beginning, in the silent records of an 

 era that must have long preceded his own introduction to a 

 world, of which, with all his boasted science, he knows so 

 little. The fabled phcenix of ancient philosophy was but a 

 type of the perpetual reinstalment of living being from 

 matter which had lived, and lived before. The lowest 

 orders of plants only can subsist upon the crude elements 

 and their simpler combinations : the higher, and more espe- 

 cially those whose seeds and leaves and roots teem with 

 sustenance for man and his animal associates, require for 

 their support particles which have already been under the 

 vital influence in some pre-existent form. And these are 

 copiously supplied. Is a rock projected from a volcano, or 

 a stream of lava cooled upon its sides — is the stone quarried 

 out of the bowels of the earth, and raised into a lofty 

 building upon its surface — vegetation will not long be 

 wanting to clothe them all ; but it will commence with the 

 simplest of its forms — with plants so minute, that even the 

 practised eye of the botanist will scarcely detect their 

 presence, unless with the assistance of his microscopic 

 glasses. Generation after generation of these mere points 

 in creation must spring there, and pass away, before the 

 grass and the wall-flower and the rock-rose can find food 

 and .a resting-place ; and myriads after myriads of these 

 must vegetate and wither on the deepening soil, before it 

 can yield the richer harvest of cultivation. Is a forest of 

 oaks to be raised upon the plain or the hillside— is the 

 corn-field to lift its golden grain, or the garden to bloom 

 redolent with beauty or utility to man — Nature must have 

 worked for ages to accumulate, above the hard a'-d barren 

 surface of the rock, the rounded gravel, p'-". the yielding 

 sand, a mass of matter diff'ering from them all, and which, 

 having once been organized, needs not again to be filtered 

 through the varied forms which originally appropriated and 

 progressively moulded it for the purposes of fertility. 



The earliest pioneers of terrestrial vegetation are, everj-- 

 where, the lichens ; a numerous and diversified tribe ; the 

 individuals of which present every variation of structure, 

 from the solitary microscopic cell, self-multiplying, to that 

 of highly-organized membranaceous and intricately-branched 

 bodies, bearingacomplicated fructification. A parallel series 



