370 
L. H. MACDANIELS 
Piperaceae 
Piper Cubeba (R.) 
Fagaceae 
Fagus sylvatica (DJ.) 
Ulmaceae 
Ulmiis effusa (L.) 
U. montana (R.) 
Moraceae (L.) 
Madura (D.) 
Ficus macrophylla (R.) 
F. stipulacea (R.) 
F. carica (R.D.) 
Artocarpaceae (L.) 
Berberidaceae (L.) 
Anonaceae 
Anona Chierimolia (R.) 
Ranunculaceae 
Atragene (R.) 
Rosaceae 
Spiraea (L.) 
Rosa (L.R.J.) 
Amygdaleae (L.) 
Leguminosae 
" Papilionaceae " (L.) (R.) 
Table 2 
Cytisus (R.) 
Robinia (S.) 
Halimodendron (R.) 
Simarubaceae 
Ailanthus glandulosa (L.) 
Malpighiaceae (L.) 
Buxaceae 
Buxus (L.) 
Coriariaceae 
Coriaria (R.) 
Anacardiaceae 
Pistacia (L.) 
Aquifoliaceae 
Ilex aquifolium (R.) 
Rhamnaceae (L.) 
Vitaceae 
Vitis canescens (L.) 
Sterculiaceae (L.) 
Cornaceae (L.) 
Oleaceae 
Fraxinus excelsior (R.) 
Asclepiadaceae 
Asclepias (L.) 
Verbenaceae (L.) 
It is readily seen by a study of tables i and 2 that transverse sieve 
plates are present in many genera of woody dicotyledons without 
reference to their phylogenetic position. Not only is there no gradual 
transition in type from the lowest to the highest, but further, in many 
families and even in some genera the type of sieve tube is not constant. 
High and low types of sieve tubes follow each other without any ap- 
parent correlation. Thus in Fagus and the Urticaceae, where low 
types might be expected, we find the single transverse sieve plate to be 
of universal occurrence, whereas in the Caprifoliaceae the sieve tube is 
definitely of type i. 
Variation in sieve-tube type within families is in some cases very 
striking. For example, in the Fagaceae the genus Fagus stands out 
as belonging to type 3, among genera of lower type. In the Cor- 
naceae, the genus Nyssa has sieve tubes of type i, whereas Cornus has 
sieve tubes almost entirely of the third type. 
The woody Rosaceae and Leguminosae are additional examples. 
In the former, Pyrus Malus and Primus serotina show sieve tubes of 
types I and 2 respectively, whereas Primus Persica has sieve tubes of 
type 3 with few exceptions (fig. 28). In the tribe Caesalpinoideae of 
the Leguminosae type 2 prevails in Gleditsia triacanthos and Gym- 
nocladiis dioica, but in the tribe Papilionoideae type 3 is the rule, as 
