110 Proceedings of the Royal Society 
These after some time presented an annnlated appearance, as 
shown in the preceding woodcut. Buds then began to arise from 
the rounded end of the leaf-stalk. In the woodcut a young 
shoot is shown arising from the petiole. Mr Lindsay tried to 
get buds from the leaves by simply placing them flat on the soil 
(like those of Bryopliyllum and Gesnera ), but in this he did not 
succeed. He found, however, that if the upper part of the leaf 
was cut off transversely, and the petiole was planted with only 
the lower half of the lamina attached to it, the growth of 
roots went on. But the upper half of the leaf when planted 
did not root. He also ascertained that, by cutting the leaf longi- 
tudinally through the midrib, and planting each half, he was able 
to get roots and buds from each of the halves after the wounds 
had cicatrised. 
These experiments of Mr Lindsay demonstrate the facility with 
which Ipecacuan may be cultivated, and they supply useful hints 
to those who are superintending the growth of Ipecacuan. 
Fresh specimens were produced, showing the result of Mr 
Lindsay’s experiments, and drawings were exhibited, which had 
been executed by Mr Francis M. Caird, one of the assistants in 
the Botanical Class of the University. 
Explanation of Woodcut. 
Ipecacuan Leaf with Petiole, Annulate! Boot, and young Plant. (From 
a drawing by Mr F. M. Caird.) 
a. Lamina or blade of leaf. 
b. Petiole or leaf-stalk. 
c. Swelling at the end of the petiole after being placed in the soil. 
d. Boot proceeding from the swelling, showing an annulated form. 
e. Young Plant arising from the swelling of the petiole. 
3. On the Physiological Action of Light. No. II. By James 
Lewar, Esq., and John G. MTCendrick, M.D. 
Since the date of the first communication, we have endeavoured 
to obtain quantitative results involving time as a variable element 
in the case of the action of light on the retina and optic nerve. 
We have therefore found it necessary to construct a true graphical 
