Syncotyly and Schizocotyly . 803 
teratological amphisyncotyly ; but the ordinary form of syncotyly occurring 
as an abnormality in apocotylous species appears to be extremely rare as 
a normal feature. 
A noteworthy feature of practically all the tube-forming species on 
record is that the seeds are ‘ albuminous ’ ; the embryo is small, usually 
straight, and develops in a homogeneous medium, the endosperm. 1 Em- 
bryogeny is likely to be symmetrical under such conditions ; and whether 
or no the presence of endosperm is conducive to concrescence of cotyledons, 
it seems probable that if such concrescence occurred at all it would affect 
both edges of the cotyledons equally. The rarity of one-sided syncotyly 
as a normal feature is therefore intelligible. 
On the other hand, a remarkable feature of the species which are 
normally apocotylous, but occasionally produce syncotyls, is that the great 
majority of them have ‘ ex albuminous' seeds. 2 The normally monocotylous 
Dicotyledons, about which there is doubt as to the means of reduction, are 
largely exalbuminous, and in many of these the probabilities are apparently 
in favour of a heterocotylous origin. 3 
The conclusions which may be drawn from these facts are — 
3. Syncotyly occurs in a great variety of species, normally or terato- 
logically. 
2. In species with albuminous seeds syncotyly usually gives rise to 
a symmetrical cotyledonary tube. 
3. In species with exalbuminous seeds syncotyly is usually asym- 
metrical, the cotyledons uniting along one edge only. 
4. The reason for (2) is probably the homogeneity of the surroundings 
of the embryo before germination, for (3) the asymmetry of its environment 
which produces accumbency and other irregularities. 
Leaving on one side the Spadicifloreae whose monocotyly is very 
possibly heterocotylous, there can be little doubt that the Helobieae include 
those Monocotyledons which are most closely allied to such admittedly 
1 The only exceptions to this rule in the long lists of tube-forming Dicotyledons given by Holm 
(’99, p. 422) and Miss Sargant (’03, p. 73) are Serratula radiata , Limnanthes Douglasii, Cardamine 
spp., and perhaps Megarrhiza californica. (See Sargant, (’03), p. 83.) 
2 An examination of the species mentioned by de Vries (’ll, p. 457 et seq.) and other authors 
as yielding occasional syncotyls reveals the fact that out of about thirty-seven species in which the 
anomaly is known to occur only the following six have the embryo surrounded by endosperm in 
the seeds : Silene hirsuta , Phacelia tanacetifolia , Anagallis grandi/lora, Polygonum Fagopyrwn , 
Mercurialis annua , Urtica dioica. 
Syncotyly is also recorded in Coniferae, often accompanying polycotyly. The most striking 
example was observed by T. G. Hill and de Fraine (’08, p. 706) in a seedling of Widdringtonia 
Whytei , whose two cotyledons were fused nearly to their tips — a feature which the authors compare 
with the double needle of Sciadopitys. The anatomy was unaffected. 
3 See Miss Sargant’s list (’03, p. 76). Abortion or displacement ol a cotyledon seems to have 
been the probable cause in the Corydalis spp., Ranunculus Picaria, Carum Bulbocastanum, Pingui- 
cula spp., and Abronia spp. 
