132 Botanisches Centralblatt. — Beiheft 2. 



Furthermore in regard to the structure of the fruit, we have 

 Seen that the dehiscent utricle of Sporolohus is common to species 

 from very diverse localities; that the long and triple-awned llowe- 

 ring glurae which tightly encloses the caryopsis in Arisiida is also 

 common to species from plains, prairies etc. ; while other genera 

 from these same places are destitute of such means for dispersing 

 their seeds, Glyceria, Distichiis, üchedonnardns etc. 



Aristida fasciculata is, thus, associated with many and very 

 diverse types of Gramineae, all of which would have been classi- 

 lied as „Xerophytes" unless the structure of other Aristidae had 

 been considered at the same time in connection with their respec- 

 tive associates. It can hardly be denied that the similarity in 

 structure, as exhibited by these plants, is too striking for sepa- 

 rating them in such classes as Xerophytes, Halophytes or Mesophytes 

 only on account of the conditions of the local surroundings, in- 

 asmuch as this same structure is illustrated by inhabitants of plains, 

 fields, swamps etc. with no modification of importance. 



Very suggestive papers have been published in later years 

 bearing upon such Classification and defining the social occurrence 

 of certain plant-species as constituting special societies. It may 

 be that such exist, but we consider it a general mistake to esta- 

 blish such societies as xerophilous, hydrophilous etc. without pre- 

 viously having studied their structural peculiarities. And the study 

 of a Single order or even a single, but large genus with wide 

 distribution, may enable us to demonstra*e such modifications as 

 are probably the result ot the influence of the enviroument, climate 

 and soil. Furthermore by extending the research to a group of 

 allies and associates a still more compleie illu -tration may be obtained, 

 than if we undertake to examine a large number of diverse types, 

 representatives of Orders, that are in no respect allied to each 

 other, but which have tbat one peculiarity in common, that they 

 are able to thrive in the same soil, in deserts, sand- dunes, bogs, 

 woods etc. 



Our present knowledge of plant-anatomy is too incomplete to 

 enable us to distinguish between such structures as are characte- 

 ristic of bog plants, of strand-plants, desert-plants etc. This be- 

 comes the more evident when we compare the works, that have 

 been published on this subject, where the author generally arrives 

 at the conclusion that no clear distinction can be drawn between 

 such and such society, as was at first considered as being perfectly 

 natural and well defined. And it is now openly admitted that 

 Halophytes and Xerophytes exhibit „prominent" or even „complete" 

 agreements as to their structure, besides that one of the most 

 prominent writers on this subject has lately expressed the opinion, 

 that it is far from certain whether any characters really exist that 

 may he defined as typical of Xerophytes and Halophytes *). 

 Moreover this same author has pointed out the remarkable large 



*) Warminp, Eug., Halophyt-Studier. (Kgl. Danske Videnak. Selsk. 

 Skr. Vol VIII. Series 6. p. 236. Kjöbenhavn 1897.) 



