799 
Syncotyly and Schizocotyly. 
Syncotyl E. Complete syncotyly obtained here, as in Syncotyl D, 
accompanied, however, by a further reduction. One of the triads had here 
lost the metaxylem group towards the line of fusion. Thus the seed-leaf 
traces consisted of (i) a normal ‘ double bundle ’ ; (ii) a e double bundle ’ with 
only one metaxylem group and a protoxylem ; (iii) a lateral bundle ; (iv) an 
accessory cotyledon trace (Fig. 19). The root was triarch, as usual in all 
except slight degrees of syncotyly. It is doubtful whether this asymmetrical 
elimination of a single metaxylem should be considered as a stage in the 
series of reductions and compressions following upon syncotyly ; this was 
the only example of the kind seen, most of the advanced syncotyls 
approximating to type D. 
Other Types of Structure. The syncotyls are frequently misshapen 
and twisted owing to difficulties in the process. of extraction from the testa, 
growth inequalities, and, later, obstruction to the plumule. The anatomy 
often reflects these deformations, and examples were studied whose structure 
it was found impossible to relate to the normal syncotylous series. No 
useful purpose would be served by describing these seedlings, whose whole 
appearance was rather pathological than teratological. 
In one seedling an accessory bundle (‘ Zwischenstrang ’) was prolonged 
downwards into the root, there giving rise to an additional xylem pole. 
This was in an example of advanced syncotyly whose root would normally 
have been triarch, but that the addition of the accessory strand rendered it 
tetrarch. A similar occurrence in a dicotyl would produce a pentarch root, 
and pentarchy has actually been recorded in Helianthus annuus by Kattein ; 1 
but in this case it appears that the accessory strand was fused with the 
adjacent lateral cotyledon trace. 
The effects of syncotyly in Helianthus annuus are therefore as follows, 
according to the degree of fusion : 
(i) Retardation of division of the lateral cotyledon trace on the side 
of fusion. 
(ii) Elimination of this lateral cotyledon trace, reduction to triarchy. 
(iii) Compression of the triads towards the line of fusion. 
(iv) Partial union of adjacent triad metaxylems. 
(v) ? Elimination of one of the triad metaxylems towards the symphysis. 
Prunus domestica. 
Examples of dicotyls and syncotyls of certain cultivated Plums were 
given me by Mr. W. O. Backhouse, of the John Innes Horticultural Institute : 
these exhibit a state of affairs much the same as in Helianthus annuus 
syncotyleus. The dicotyl is tetrarch, and each cotyledon takes a median 
1 Kattein (’97), p. 129 . The structure of tetrarch seedlings is also described, but no notice is 
taken of the median polar protoxylems of the triads. 
