104 
Lee . — The Morphology of Leaf-fall. 
Acer pseudo-platanus, Linn. 
(b) Ribes sanguineum, Pursh. 
Ribes nigrum, Linn. 
Diospyrus virginiana, Linn. 
Halesia tetraptera, Linn. 
Forsythia Fortunei, Hort. 
(= F. suspensa, Vahl). 
Baccharis halimifolia, Linn. 
Gleditschia triacanthos, Linn. 
Robinia Pseudacacia, Linn. 
Clerodendron trichotomum, 
Thunb. 
Class II. 
(a) Tilia europaea, Linn. 
Corylus Colurna, Linn. 
Cercis Siliquastrum, Linn. 
Carpinus Betulus, Linn. 
Prunus Cerasus, Linn. 
„ virginiana, Linn. 
„ communis-dulcis. 
( b ) Betula verrucosa, Ehr. 
Platanus orientalis, Linn. 
Rhus typhina, Linn . 
Broussonetia papyrifera, Vent. 
Plcus Carica, Linn. 
Morus alba, Linn. 
Morus nigra, Linn. 
Juglans nigra, Linn. 
„ regia, Linn. 
„ rupestris, Engelm. 
Cornus sanguinea, Linn. 
„ Mas, Linn. 
Nyssa sylvatica, Marsh. 
Ailanthus glandulosa, Desf. 
Celastrus articulatus, Thanb. 
Phellodendron amurense, Rupr. 
Fraxinus excelsior, Linn. 
Catalpa Kaempferi, Sieb. 
Liriodendron tulipifera, Linn. 
Class III. 
Salix Caprea, Linn. Populus balsamifera, Linn. 
The protection of the tissues of the stem underlying the scar is aided by 
the production at a later date of a layer of cork cells which subsequently 
becomes continuous with the periderm of the stem. 
In many species the persistent leaf or leaf-scar is thrown off during the 
second year. 
The above investigation was commenced at the suggestion of Professor 
J. B. Farmer, F.R.S., to whom the author is sincerely grateful for constant 
advice and encouragement during the progress of the research. 
Appendix. 
It has been thought better to give a separate description of the methods 
employed in this research. The material was collected in July, August, 
September, October, and November, chiefly in the year 1909, and was 
preserved in 70 per cent, alcohol. Both longitudinal and transverse sections 
of the leaf-base were taken, chiefly by hand but also with the microtome, 
and these were stained with several of the common double stains. For the 
