316 PROF. F. О. BOWER ON APOSPORY AND ALLIED PHENOMENA. 
examples as the Rhizocarps and Selaginella, and among Ше Phanerogams conspicuous 
cases such as Gnetum* and Rosa livida Т. 
If weapply the definition of ** sporal arrest " with strictness to the Phanerogams, then 
there would be included a host of teratological forms, which show, not only arrest of 
spore-formation, but also substitutionary growths, which are apt to mask the actual 
phenomena of arrest. It is unnecessary now to enter upon the detailed discussion of 
these, though they should be remembered in connection with the cases above noted. 
From what has now been said it will be seen that sporal arrest, whether partial or com- 
plete, is a wide-spread phenomenon, and is to be found in one form or another among 
plants ranging from the Mosses to the Dicotyledons. 
We may now proceed to consider the nature of those substitutionary growths which 
frequently follow **sporalarrest;" and often may, in one way or another, supply the 
place of spore-formation, as regards the propagation of the plant. But, as above pointed 
out, the appearance of substitutionary growths does not seem to be a necessary conse- 
quence of the arrest of spore-formation; still it is found to occur in a large number of 
cases, and the two phenomena are no doubt closely related to one another. When 
the arrest of one member of a system is followed by the excessive development of 
another, a “correlation of growth” is said to exist; this correlation has been expe- 
mentally demonstrated in the case of various parts of the vegetative system by Goebel }; 
the appearance of substitutionary growths following sporal arrest points to the existence 
of a similar correlation of growth in these cases also, and this has been specially recog- 
nized by Goebel in recent articles on the doubling of flowers $, and on the fertile cones 
of the Equiseta ||. 
As the substitutionary or correlative growths are of various nature in different cases, it 
will be necessary to classify them, and they may be ranged under three heads: 1, simple 
prolification; 2, sporophoric budding; and 3, apospory. Under the first head will fall 
those examples of extra growth of the single floral shoot or flower associated with sporal 
arrest, in whieh the normal order and succession of parts of the vegetative system is 
continued or, after some irrregularities, resumed; under the head of sporophoric budding 
would be included all cases of formation of new buds of а sporophoric character following 
on partial or complete sporal arrest; while the term apospory is applied to those cases 
where sporal arrest is followed by developments of an oophorie character, resulting from 
direct vegetative outgrowth from thesporophore. Simple prolification is the most direct 
form in which a substitutionary or correlative growth can present itself; the activity 
which should, under normal circumstances, be devoted to spore-formation, appears here 
to be diverted into a purely vegetative channel, and makes itself apparent in the con- 
tinued growth of the shoot, and even in the formation of fresh lateral organs on the 
* Strasburger, * Angiospermen u. Gymnospermen,’ p. 116, &c., Taf. xiii., xiv. 
T Strasburger, 1. с. р. 14, Taf. iv., v. 
$ Bot. Zeit. 1880, р. 753, «с. 
$ “ Beiträge zur Kenntniss gefüllter Blüthen," Pringsheim's Jahrb. vol. xvii. p. 207. 
|| Berichte der Deutschen. Bot. Gesellsch. 1886, p. 134, 
