Allgemeines. !<)/ 



Farmeria is closely allied to Hydrobryum with the chief difference 

 that the fruit does not dehisce, but remains tightly held down vvithin the 

 hard, persistent bracts. The 2—4 seeds germinate within the fruit, the 

 seedlings breaking through the thin fruit-walls. In this genus the seedling 

 itself shows dorsiventrality. The primary axis rarely forms more than 

 6 — 8 leaves; thallus and secondary shoots resemble those of Hydrobryum. 

 In the flower the biioeular ovary is strongly dorsiventral, the lower 

 loculus being more or less abortive; only 2 or 4 ovules are formed in 

 the other. The flower is quite prostrate as in Hydrobryum sessilc, only 

 the stigmas and the long stamen bending üpwards out of the spathe. 



Rejuvenescence, i. e. formation of new growing points if 

 the old ones are damaged, probabiy occurs in all the genera 

 discussecl. A number of anatomical details are given in the 

 course of the paper, which I have had to entirely neglect. The 

 absence of intercellular Spaces and the abundant occurrence of 

 silica should be noted. 



The general snmmary and discussion, which follows the 

 special part of the paper and which is concerned more or less 

 with all the Podostemaceae, is included under a nnmber of 

 different headings and is of course in part a repetition of what 

 has gone before. Only a few points can be mentioned here. 

 The thallus with its secondary shoots is regarded „as probabiy 

 adapted less to the rushing water as such than to the dangers 

 inseparable from life in such water, i. e. chiefly the ever present 

 risk of exposure by the shallowing of the water, but also 

 perhaps the increased scour. The more highly modified the 

 thallus, the swifter on the whole is the water in which it lives." 

 The capacity of rejuvenescence may be also regarded as an 

 adaptation to the mode of life. 



In the discussion of the marked dorsiventrality of the 

 Podostemaceae the author concludes that „the dorsiventrality 

 of the flowers, which is the most important morphological 

 character in the Classification of this order, is a direct result of, 

 or in direct correlation with, that of the vegetative organs". 

 Further that it is „most probable that to a large extent dorsi- 

 ventrality in the floral organs is due, not to natural selection 

 in reference to the Performance of the functions of the flowers, 

 but to the direct action of other causes, and that directly or 

 indirectly it is mainly the result of dorsiventrality of the vegetative 

 organs and horizontal position in development." If a character 

 can be thus forced upon an organ, „it seems only likely that 

 other characters may have been forced upon the same or other 

 organs in similar or other ways, and consequently that the 

 study of adaptation must be accompanied and checked by the 

 study of experimental and comparative morphology, and of 

 Variation and correlation." The question is also raised as to 

 whether many of our species, genera, tribes, etc. are not poly- 

 phyletic. „It is quite possible that species not at all closely 

 allied may take the same generic step, which brings them close 

 together in our schemes of Classification, though their immediate 

 ancestors might have been far apart by the criteria tised." 



