THE FERNS (EILICALES) 
265 
recapitulatory. However, uo finality is claimed, “ Evolution has 
followed lines of opportunism not of logic ” ; and would-be stelists 
may follow up the copious literature quoted with this section (66 
references). 
Discussion of the spore-producing organs follows the lines of the 
author’s previous work (Land Flora, 1908), involving the Simple, 
Gradate, and Mixed Sorus. The primitive sporangium is taken as 
terminal or marginal, and the superficial position as derivative— 
following increase of lamina-surface in a “ phvletic slide.” The story 
of the sporangium is again familiar, with its stages of annulus- 
progression and restriction of spore-output. Little evidence of com¬ 
parative value is gleaned from the prothallus with its archegonia, 
antheridia and embryology ; but older interpretations of the importance 
of the octant-embryo are discarded. Special prominence is now 
attached to the story of the suspensor, which is regarded as probably 
very primitive for the Fern phylum ; this view regarding again the 
prothallus as originally a massive structure, while the embryo nursed 
within it is conceived as “ a simple leafy shoot from the first.” A 
short chapter deals with abnormalities, apospory, apogamy, reversional 
teratology, and the total list of papers quoted so far extends to over 
300; these being very conveniently numbered in sequence, and given 
at the end of the respective sections. 
In a concluding chapter Professor Bower draws together the threads 
of his argument, in getting down to the Archetype of the Ferns 
which is to be the basis of further synthetic treatment of the 
group. In this he is less happy than in dealing with facts and 
figures of the general text, if only because in writing but a part of a 
general series of volumes he wishes to avoid poaching on the preserves 
of other writers; and little can be said of any one group of plants on 
internal evidence alone, any more than in age-long discussions of the 
origin of man from data confined to the human race. However, by 
adding together the conclusions of the preceding chapters, it is 
suggested that one may “contemplate the primitive Fern Sporophyte 
as a simple, upright, radial, rootless shoot, either unbranched or 
showing dichotomy ” (though it is not clear how such a plant 
managed either to stand up or to get its water-supplies). The primi¬ 
tive fern-leaf is “ figured as long-stalked, with a distal dichotomy of 
narrow, separate, single-veined segments, arranged either radially or 
bifacially,” again “ relatively robust in primary organization of 
parts,” with simple stelar strands, and bearing distal or marginal 
sori, the primitive sporangium large and eusporangiate. In fact, one 
begins to sense HJiynia in the offing, rather than “the spindle-shaped 
embryo giving off enations ” of The Land Llora (1908). Students 
who have long felt the difficulty of cooking a Fern-type from the 
model of Lycopodium Selayo will be pleased with this alternative 
“ reasonably tenable hypothesis.” It is, of course, “ not even sug¬ 
gested that the Psilophytales include the direct ancestry of the 
Filicales ” ; but homoplasy affords a convenient key to much ancient 
land-vegetation. Such little things as the origin of the root, or the 
phvllotaxis-system which differentiates leaf-members from branches 
are lightly got over. 
Journal or Botany.—Yol. 61. [October, 1923.] 
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