Segmentation of the Stem . 5 
level. Thus in mericyclic articulation the Sprossglieder are 
juxtaposed , in holocyclic, superposed. 
Chapter II. is devoted to the origin of the stem with holocyclic 
“Sprossglieder.” After citing various authors, including Delpino in 
his work on Phyllotaxy, who have intuitively held the “ Sprossglied” 
theory, he refers to the two categories of independently developed 
“Sprossglieder,” viz. (1) an axillary shoot reduced to the first 
“Sprossglied” ( i.e. a leaf with its stem-joint) as in the male flower 
of Lemna, Zannichellia, Najas, Casuarina, in which the stem-joint 
is indistinguishable from the filament; in the female flower of 
Balanopliora , Araucaria , Podocarpeas, Ginkgo , Typha ; and in the 
vegetative shoot of Lemna : (2) the “ Sprossglieder ” of a sympodium 
where each ends in a terminal leaf, an analogy with which is found 
in the sympodia of Ampel-opsis , the inflorescence of Boraginacese, etc. 
In the monocotyledonous embryo, as Hanstein has shewn, the 
cotyledon is a leaf terminal to the hypocotyl, hence Nageli, Sachs, 
and Leitgeb were led to regard the whole embryo as a thallus. E. 
Fleischer and F. Hegelmaier (in work which has been ignored by 
our text-books) shewed that the second phase in the development 
of the embryo consisted in the development at the base of the 
cotyledon of a protuberance whose upper part became a terminal 
leaf and its base a “ Stengelglied,” out of which arises the next 
protuberance; ‘the stem is built up of a succession of generations 
• of independent “ Stengelglieder” springing laterally from an 
antecedent “Stengelglied,” in fact a sympodium of “Sprossglieder,”’ 
until eventually an apical growing point is formed. Previous to the 
formation of this latter an axis is not present, so that Al. Braun 
erred in stating that the theory of phyllotaxis demands the presence 
of a stem as a basis on which the leaves may arise, as also did 
Sachs and others in holding the view that leaves always arise 
laterally on a previously-fo med axis. 
Comparative development unequivocally shews, according to 
Celakovsky, that the monocotyledonous embryo is a vegetative trans¬ 
formation of the Bryophytic sporogonium, and each “Sprossglied” 
is a repetition of this latter. The incipient stages in the branching 
of the monocotyledonous embryo the author terms pleuroblastic, its 
subsequent branching and the growth of the higher plants generally, 
he terms acroblastic , these two, i.e. the formation of an embryonic 
shoot by means of a succession of “Sprossglieder,” and that by 
