An Historical Sketch. 
79 
We have thus been able to trace the homologue of the ovule in three 
great phyla of the vegetable kingdom ; and this is only what one would 
a priori expect, for if there is a unity underlying vegetable life, and if all 
forms of plant-life own a common origin in the far past, the same organs, 
under a more or less modified or disguised form, will be produced by 
plants belonging to most of the great phyla of evolution. 
Finally, some of the objections urged by Celakovsky against the other 
two theories of the ovule may be brought forward. 
Against the bud-theory may be placed the fact that in almost all cases 
the integuments arise basipetally and not acropetally, a strange and ex- 
ceptional state of affairs if they really represent foliar appendages of the 
nucellus. Eichler, Schmitz, and at one time Warming, held that the 
terminal organs belong to the caulome-category on account of their 
position ; but this reliance on topical morphology is useless, as terminal 
organs other than axes are known. Hanstein showed that where the apex 
of the stem ceases to grow the apical periblem continues to do so and 
forms a terminal organ, which is a leaf, as the latter is always formed 
from periblem, whereas it is by growth of the plerome in length that an 
axis is continued in growth. The terminal cotyledon of Monocotyledons 
is another case in point. Thus, terminal ovules are not necessarily axial in 
nature. As regards the occurrence of adventitious buds in connexion with 
the ovules, our author determines, as far as his own investigations on 
Alliaria are concerned (Fig. 9), that the bud always represents a patho- 
logical new formation, and not a transformation of the ovule ; he found 
never a trace of an axis on which integuments are borne as lateral 
leaves. 
He enters into a lengthy criticism of Peyritsch’s views and observa- 
tions, which is in itself of considerable value towards the further elucidation 
of the nature of the ovule. The conclusions of this author, that the 
adventitious shoots are derived from and homologous with ovules, is shown 
to be groundless. 
Celakovsky says : £ It may be stated with certainty that shoots replacing 
ovules are never met with in virescent structures, and much less is this the 
case with transitions between ovules and such shoots.’ 
Peyritsch’s study of ovular metamorphosis is throughout influenced by 
the idea that the nature of the ovule can be determined from developmental 
data. He regards the ovular rudiment and the nucellus as identical 
(shown by Warming to be incorrect) ; that, therefore, the nucellus arises 
directly on the placenta and bears the integuments : but this never 
happens. He thinks, further, that the terminal ovule of Rumex scutatus 
is a shoot owing to its position ; but it is no more so than is a terminal 
nucellus. 
Other criticisms of Peyritsch’s observations and theories could be 
