14 BRAUN, ON UNICELH]IiA.R AI,G.^. 



which, among the vascular cryptogams, the pro-embryo or 

 prothaUmm corresponds. After fecundation, there arises from 

 these transitory primordia another and principal series of 

 vegetable generations, commencing from the embryo, and pro- 

 ducing the vegetative stirps, by whose evolution in opposite 

 directions the differences of root, stem, and leaves are produced. 

 Subsequently, in the ascending portion of the stirps the mor- 

 phosis of the plant is continued, and those stages of the process 

 appertaining to the vegetative life having been established, it 

 passes into a new stage by the formation of the flower, and by 

 the intervention of the flower ultimately attains to the object 

 of the whole vegetation in the production of the fruit. 



A similar kind of gradation is exhibited in the vegetable 

 kingdom taken as a whole. This begins, as is obvious, in the 

 more simple plants, which present only trifling distinction of 

 organs either external or internal, the root, stem, and leaves 

 being either, as it were, fused together or ambiguous. They 

 have neither flower nor any true fi'uit; the organs of fructifi- 

 cation are closely connected -with those of vegetation, and the 

 act of fecundation, if any take place, is competent merely to 

 excite, as it were, the first stage of evolution of the plant, 

 since there is no succeeding generation whatever. 



To this category belong the lower cryptogamous plants, 

 aphyllous or simply cellular, and which have been, not inap- 

 propriately, termed by recent writers— p7'otopJ/ytes or thallo- 

 phytes. They represent, as it were, the pro-embryos of the 

 higher plants, and constitute, in fact, the primordial vegeta- 

 tion in protogaean history, as well as in the existing economy 

 of nature, forming the broad foundation of the whole vegetable 

 kingdom. 



This primary division in the natural system is succeeded 

 by another, characterised by a heteromorphous, duplex vege- 

 tation, for a knowledge of Avliich we are especially indebted to 

 the discoveries of recent observers ; for to the primary and 

 transitional vegetation, that is to say, to a homogeneous pro- 

 thallium, aphyllous and merely cellular, fecundation being 

 completed in the protliallium itself, succeeds another, charac- 

 terised by the distinct formation of external parts (stem, root, 

 and leaves), as well as by the constitution of the internal 

 texture composed of a mixture of cells and vessels. Thus 

 from a lower stage the vegetation is advanced by successive 

 generation to a liigher, but without its ever attaining to the 

 ultimate goal, inasmuch as plants belonging to this division, 

 in which the progress of the metamorphosis is interrupted, 

 and remains at the stage of a vegetative stirps, never arrive 

 at the production of flower and fruit distinct from the vege- 



