An Histoi'ical Sketch. 
63 
cannot have the same morphological meaning. The ovule does not always 
possess the same morphological value.’ The idea of an ovule, he thinks, 
only includes a tissue which encloses the embryo-sac and nothing more ; 
and there need necessarily be no differentiation into integument and 
nucellus. ‘ The origin of the embryo-sac is not confined to the members 
of a definite morphological category.’ He considers that the ovule in 
Piperaceae represents a continuation of the axis of the flower 1 , the integu- 
ments being its leaves, and equivalent to the carpels and stamens. In 
order to form the ovule the apical portion of the axis undergoes a meta- 
morphosis through the disappearance of all internal differentiation ; the 
integuments arise basipetally ; and on these grounds he regards the ovule 
as a new structure , for it cannot be made to fit into the morphological 
categories of caulome, phyllome, or trichome. From this author’s views on 
the nature of the ovule generally, it appears justifiable to include his name 
under our present heading. 
Sachs (51), in the second edition of his Textbook, enunciates a very 
similar view ; on p. 573 (Eng. ed.) he says : c I am induced to ascribe 
different morphological significations to the ovules, according to their mode 
of origin and their position.’ On p. 575, after citing the various theories 
held up to that time on the ovule, he says : ‘ Of these views, the one which 
appears to be most true to nature is the one which allows the greatest 
latitude ; but it is not always possible to refer an ovule to one of the 
categories, caulome and phyllome, for its position does not necessarily 
indicate its morphological significance. Thus a lateral ovule, as in Com- 
positae and Primulaceae, might be either a leaf or a bud ; its probable 
leaf-nature in these cases depends entirely on teratological evidence, which 
is of very doubtful value, for an organ in a monstrous condition does not 
necessarily assume its primitive archetypal form.’ The following sentence 
affords us the key to his whole position and characteristic view of the 
matter : f The difficulties met with in endeavouring to regard the ovule as 
a caulome or phyllome may be transcended by regarding it as an “ emergence” 
borne sometimes on an axial, sometimes on a foliar member.’ (This is 
practically equivalent to regarding it as an organ sui generis.) 
Strasburger (47), in his time, has held two distinct theories on the 
subject ; the earliest of these, embodied in his classical work, ‘ Die Coniferen 
und Gnetaceen,’ supported the position of Braun and Payer. This view 
arose naturally from his researches on the Gymnosperms, the ovule of 
which he regarded as a metamorphosed bud whose stem was the nucellus 
and the integuments the leaves. But in course of time his views changed, 
until in ‘Die Angiospermen und die Gymnospermen ’ we find him fully 
qualified for being classed among those who support the sui generis theory 
of the ovule, in regarding the latter as homologous with an independent 
1 In this order the single ovule terminates the floral axis. 
