RE.rUVENESCKNOF, IN NATURE. 129 



in the horizontal branchlets are formed, in each case, one 

 thick-coated, resting spore.* Bryopsis goes still further 

 than Vmccheria in the development of different parts 

 from one and the same cell; for in this the cell 

 produces roots on one side, and, on the other, erect 

 stems, with apical growth, multiplying themselves by 

 ramification. On these stems are formed distichous, or 

 spiral series of shorter branchlets, with limited apical 

 growth, these clothing the stem like leaves, and finally, 

 when the canal of communication with the stem has 

 become closed up, falling off" like leaves. The numerous 

 moving germ-cells of Bryopsis^ are formed in these 

 branchlets. The genus CaulerpaX forms the last link in 

 this series of remarkable shapings of the simple cell. 

 In this the undivided cell forms in its development a 

 creeping stem, growing on ad infinitum at its apex, 

 from which (besides inessential branches, repeating the 

 main stem, and, like it, unlimited,) proceed two kinds of 

 branches with limited growth, different from each other 

 and from the main stem, namely, to the under side 

 divided roots, to the upper leaf-like branches which, 

 originally cylindrical, expand into laminae in subsequent 

 growth, and present different forms according to the 

 species; in Caulerpa prolifera, for example. Ungulate and 

 obtuse, in C. denticulata\ broadly lanceolate, deeply 

 toothed, and somewhat acute, in C. plumaris pinnatifid 

 or cut like a comb. Much as these structures remind us, 

 by their form, of the stem-leaves of the higher plants, 

 they are merely hollow prolongations of the one cell, 



* Vaueheria, moreover, passes into a manj-celled condition in the pre- 

 paration for spore-formation, for the points of the branches on which spore- 

 formation occurs, become shut off into distinct cells. Vide Unger, 'Die 

 Pflanze in moraente der Tliierwerdung,' (1843), and Thuret, ' Sur les Organes 

 locomoteurs des Spores des Algues,' ('Ann. des So. nat.,' 1843.) 



f Vide the section on Bryopsis, in Nageli, ('AJgensysteme,' p. 171 ;) 

 'On the Formation of Spores,' J. Agardh, ('Ann. des Sc. nat.,' 1886.) 



+ Vide Nageli's important researches in Caulerpa prolifera, ('Zeitschr. 

 fur Wiss. Bot.') heft 1, (1844,) p. 134. 



§ Decaisne, 'Elantes de 1' Arabic lieureuse,' 'Arch, du Mus.' ii, (1889,) 

 t. vi, li, 



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