Certain Points in the Morphology of Frullania, dx. 471 



paper Qoc. cit.^ p. 565) lie quotes with approval the follow- 

 ing passage from Sachs {Vorlesungen, p. 48) : — " A typical 

 shoot consists of the leaves and the axis, which are not 

 really to be regarded as different organs, but fundamen- 

 tally as parts only of one organ In their nature, as 



shown by the history of their development, the leaves are 

 fundamentally nothing more than processes, or outgrowths 

 of the axis of the shoot." 



To Professor Sachs' statement I have no objection to 

 offer, as it appears to be a correct statement of fact ; but 

 if it were suggested that these parts — leaf and axis — are 

 potentially equivalent, or interchangeable, it would be pre- 

 cisely as if a zoologist were to say that in a segmented 

 animal — e.g.^ a Myriapod — the trunk-segment and its radi- 

 ating process or outgrowth the limb were potentially equi- 

 valent or interchangeable. No doubt, the trunk-segment 

 and its appendage the limb are parts only of one structure, 

 the body-segment or metamere (" /S'oma;!o?wc" of Good sir) ; 

 but no zoologist would imagine the conversion of the trunk- 

 segment into a limb, or vice versa. And it would, to my 

 mind, be equally difficult, in the plant, to imagine the 

 conversion of the axial portion of a shoot-segment into a 

 leaf, or vice versa. And still less conceivable would be the 

 conversion of a leaf, or part of a leaf, into a whole shoot, 

 involved in the supposed replacement of a petal or a stamen 

 by a whole flower, or, as in the case of Frullania, &c., the 

 replacement of an " auricle " by a whole shoot. Such con- 

 version would be comparable, in the segmented animal, to 

 that of a limb, or process from one of the body-segments 

 into a whole body built up of a number of such segments. 



A. D. 



DESCRIPTION OF PLATE XV. 

 II = Lateral leaf. 



ait = Auricle, or lower lobe of lateral leaf. 

 am = Aniphigastriuiu, or ventral leaf. 

 7/ = Lateral leaf adjacent to the origin of the branch. 

 X = Scale (of controverted homology) obliij^uely subtending the branch. 

 f = First lateral leaf of the branch. 

 rr = Rhizoids. 



Frullania Tamarisci. 



Fig. 1. Monstrosity. Shoot seen on ventral aspect, showing a branch 



obliquely subtended by a bifid aniphigastrioid scale (,r), in the 



ordinary way. The auricle {z), however, of the next lateral leaf 



vertically below that adjacent to the branch has become abnor- 



