CLASSIFICATION OF APPENDAGES 145 
difficulties: of this the Psilotaceae are.a conspicuous example, and the 
analysis of the parts composing their strobili has led to voluminous 
discussions. The difficulties are no less in the Sphenophylls and Cala- 
marians. The presumption upon which morphologists have habitually 
proceeded has been that all the parts are, or at least should be, reducible 
to certain categories, such as axis, leaf, emergence, sporangium—these 
being the headings under which the parts of the shoot in the higher 
Vascular Plants are ranged. It is possible by the use of artifices, which 
sometimes appear to be curiously strained, to carry out the classification 
of all the constituent parts of. the shoot in Phanerogams into these cate- 
gories. But is the morphologist justified by this measure of success in 
the practice of a somewhat artificial method in assuming that it shall 
always be equally applicable to all Vascular Plants? And further, is it a 
scientific method forcibly to extend the conclusions obtained from the 
study of the higher forms to the lower? The attitude of the believer in 
evolution should be the converse: to examine the lower types with a 
mind untrammelled by conceptions derived from the higher, and a termin- 
ology free to express what is actually seen in the more archaic forms. 
Subsequently his conclusions may -be extended to the higher forms. At 
the present day it will seem hardly necessary to put down such simple 
principles as these explicitly; but doing so finds its justification in the 
habit of thought, still ingrained in the science, of reading the lower Vascular 
Plants in terms of the higher, just as it was done in the pre-Darwinian 
days. From this the mind of the modern morphologist must be entirely 
free. 
The difficulty of reducing the parts of the strobilus in certain Pteri-- 
dophytes to the categories above named has already extorted from 
morphologists the adoption of a further term not yet used in reference to 
Flowering Plants. The non-committing word ‘‘sporangiophore” is now 
understood to connote a structure which bears sporangia, but is not readily 
referable to the category either of axis or leaf, though it might be included 
under some broad use of the term “emergence.” It may contain vascular 
tissue, and be inserted either on the axis or on an appendage. It will 
be the object of this chapter to consider the relations of the sporangia, 
the sporangiophores, and the sporophylls to one another, and to the axis 
of the whole strobilus, as seen in the various types of Pteridophytes. 
It is a rare thing for sporangia to be borne directly upon the axis 
itself, though there is theoretically no reason. against it, but rather the 
reverse. The Lycopodiales include forms which show this position of the 
sporangia, and Se/agined/a is usually quoted as a case in point (Fig. 74). 
It is true that here the sporangium is inserted on the axis, and springs 
directly from its tissue: it may originate as a swelling quite distinct from 
that which develops into the sporophyll ; but the sporangia are not scattered 
irregularly on the axis, for there is a constant relation of each sporangium 
to the subtending appendage: the sporangium and the sporophyll are in 
; K 
