UNITIES OF LIFE 



and systems of organs may be associated for the fulfil- 

 ment of a definite physiological task. 



In the higher animals and plants we usually regard as 

 the "real individual" (in the wider sense of the word) 

 the tissue-forming organism made up of various organs ; 

 and we may here briefly and instructively call this the 

 histonal individual (or, more briefly, the "histonal"). 

 Botanists call this individual phenomenon among the 

 metaphyta a sprout (blastiis). Zoologists give the title 

 of "person" {prosopon) to the corresponding unity 

 among the animals. The two forms agree very much in 

 their general features, and may be called "individuals 

 of the second order," if we take the cells to be the first 

 and the stock the third stage in the hierarchy of or- 

 ganic individuality. In comprising them here under the 

 general head of histonals, or histonal individuals, I mean 

 by this to designate the definite physiological unity of 

 the multicellular and tissue-forming organism, as con- 

 trasted with the unicellular protist on the one hand, and 

 the higher stem, made up of several histonals, on the 

 other. 



The plant-histonal, which Alexander Braun especially 

 clearly marked out and described as the sprout, is found 

 in two principal forms in the kingdom of the metaphyta 

 — the lower form of the layer-sprout {thalliis) and the 

 higher form of the stalk-sprout {cnlniiis). The thallus 

 predominates in the lower and older sub-kingdom of the 

 layer-plants {thallo phyta) , in the classes of the algas and 

 fungi; the culmus in the higher and younger sub-king- 

 dom of the stalk-plants UoruiopJiyta), in the classes of 

 the mosses, ferns, and flowering plants. The culmus 

 presents in general the characteristic form of an axial 

 central organ, the stalk, with lateral organs, the leaves, 

 attached to this at the sides, the former having an un- 

 limited vertical growth and the latter an unlimited basal 

 growth. The thallus does not yet show this important 



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