52 
‘have yet been reported in the literature on the subject, except 
in Dr. Smirn’s. brief statement. 
Now the hypocotyl is, so to say, the protogenic form (,Jugend- 
form”) of these plants, and these Zaeniophyllum-species may 
therefore be said to hark back continually to their protogenic 
stage, a fact not known to occur in higher plants as a normal 
fact in cevelopment. If we wish to parallel it with other phe- 
nomena in the vegetable kingdom we have to go back to cryp- 
togams, namely mosses and ferns. 
In his well-known study ,Ueber Jugendformen von Pflanzen 
und deren kiinstliche Wiederholung” Gorse. has summarised 
what is known about this matter. Also in his ,Organographie 
der Pflanzen”, the same author has dealt with this subject. I may 
therefore refer to Gorset’s studies afore mentioned for the litera- 
ture on this interesting subject. One now can partly compare the 
formation of hypocotyls in 7aeniophyllum proliferum to the re- 
generation of mosses and certain ferns. At the germination of 
the spore there is formed a body, to which is given the name 
of protonema, and on this arise buds from which the moss- 
plant proper is developed. Now it may happen that the growing 
apex of the stalk becomes transformed again into a protonema, 
and thus so tho say reverts to its primary form; Gorser reports 
this fact as occurring in Ephemeropsis, but observed the phe- 
nomenon regularly in Funaria-plants (p. 467). In Schizostegia 
osmundacea it may also occur that the vegetative, unbranched 
shoots cease growing after having formed a small number of leaves, 
then slowly decay. Now if such a stem-tip is applied, before the 
apical cell is dead, to a moist substratum, this apical cell will 
develop into a protonema-thread. The apical cell has therefore 
: changed its function and has now become similar to an ordinary 
vegetative cell. Also in these plants therefore the trend of the 
Gevelopreent of an adult plant may revert to that belonging to 
a protogenic growth and that without any transitional forms. 
eaitething similar has also been observed in ferns. Hor- 
MEISTER for instance mentioned already that in a certain plant 
i ge, a and a filament « once more into a a flat ee 
again into a filiform process,ie 
