On the Phosphorescence of Zoophytes. 257 



sap of the stem is absorbed by the gum which thereby ex- 

 pands and at length exudes from the openings ; but it appears 

 to me that the facts with which we are as yet acquainted do 

 not allow us to assume an actual motion of the gum in the 

 containing vessels. 



M. Morren assumes that this gum is formed by the meta- 

 morphosis of the amylum in the interior of the stem, and that 

 it thence passes into the frond. Although this assumption 

 appears to me as yet groundless, still I can myself bring for- 

 ward an observation which shows that a very large quantity 

 of gum is contained in the interior of the pith of the stem of 

 Encephalartos Frederici Gulielmi. A cavity had been formed 

 in the interior of the pith into which the amylum metamor- 

 phosed into gum flowed from the neighbouring cells, and was 

 collected in a considerable mass, which gradually increased 

 the size of the cavity. 



M. Morren describes moreover the position of the gum-pas- 

 sages in the frond of Cycas revoluta : they are found both in 

 the centre and in the circumference in considerable numbers, 

 and may easily be seen by means of a simple microscope in 

 every transverse section of the leaf-stalk. 



In the leaves these passages are found only on either side 

 of the nerve. M. Morren saw the ramification of a gum-pas- 

 sage in the leaf-stalk ; in the bark of the stem it was already 

 known. The former statements concerning the production 

 of the gum- vessels and on the structure are also confirmed. 

 Finally, M. de Coninck has examined chemically the gum from 

 the leaves of Cycas revoluta, but for this purpose he could not 

 obtain a perfectly pure substance : the incinerated leaves con- 

 tained 4'95 per cent, of inorganic substances consisting prin- 

 cipally of carbonate of lime, which was probably produced 

 from the oxalate ; moreover free oxalic acid was found in the 

 leaflets. 



[To be continued.] 



XXXIII. — On the Phosphorescence of Zoophytes. By the 

 Rev. David Laxdsborough, of Stevenston, in Ayrshire. 



In Dr. Johnston's ' History of British Zoophytes,' he quotes, 

 in his description of Sertularia pumila, the following passage 

 from Stewart : — " This species, and probably many others, in 

 some particular states of the atmosphere, gives out a phos- 

 phoric light in the dark. If a leaf of the above Fucus serratus 

 with the Sertularia u})on it, receive a smart stroke with a 

 stick in the dark, the whole coralline is most beautifully illu- 

 Ann. ^ Mag. N. Hist. Vol. viii. S 



