258 W. HOFMEISTER OS THE DEVELOPMENT OF ZOSTERA. 



lateral surface of the older sprout naturally follows ; as occurs 

 most clearly in the earliest rudiments of fronds, situated in de- 

 pressions of the creeping main axis, of Polypodium aureum and 

 other Ferns. But even secondary axes which become nakedly 

 visible on the originally convex outer surface of the young main 

 axis, may likewise become sheathed subsequently by the primary 

 sprout, through peculiar growth of the latter ; Isolepis affords a 

 striking proof of this. 



It need scarcely be explained that the discussion here promul- 

 gated is not and could not be anything more than an invitation 

 to repeated investigations of the different stages of development 

 of the Monocotyledonous embryo. A complete decision in 

 favour of one or other of the two views can only be obtained by 

 tracing back — a difficult task indeed — the development of the 

 seedling plant to the mode of increase of each individual cell. 



No question in the whole field of the Morphology of Plants 

 has been treated by so many persons and in such varied ways, 

 as the import of the parts of the embryo of the Monocotyle- 

 dons ; to none better applies an often misplaced quotation from 

 Goethe ; we may assert that " all possible combinations are ex- 

 hausted '^ here. Thus the idea brought forward in the foregoing 

 pages is only the repetition of an earlier one essentially similar. 

 If it be thought better grounded than that more current among 

 modern botanists, we find, in recompense for the wide separation 

 it makes between the Dicotyledons and Monocotyledons, the 

 most striking agreement of the development of the embryo of 

 the latter, with the course of the formation of the germling of 

 the Vascular Cryptogamia. As I have abundantly demon- 

 strated*, the main stem of the plant of all Vascular Cryptogams 

 is a secondary axis, arising laterally on the primary leafless 

 axis. A second and not unimportant point of comparison then 

 at once suggests itself. The Vascular Cryptogams may be 

 divided into two primary groups according as the germinating 

 plant produces the second frond below the first (below that sur- 

 face turned away from the mouth of the archegonium), or above 

 it. In the former case the first adventitious root appears simul- 

 taneously with the first frond, beside its base ; in the latter case, 



♦ See Botanische Zeitung, 1849, p. 797; " Vergleichende UntersuchungeUy 

 &c." Leipsic, 1851, pp. 85, 106, and elsewhere. 



