264 M. C. COOKE, NOTES ON PODISOMA. 



reappear again the following spring for many successive years. 

 The same parasite in the United States attacks the cedar {Juniperus 

 Virginiana). Corda,* Rabenhorst,f and some other authors, have 

 erroneously described the Podisoma as growing on dead or dying 

 branches, whereas it always appears on trees and branches which are 

 vigorous and full of life. As M. Tulasne remarks, the exuberance 

 of vegetation which they determine locally in the plant that nourishes 

 them is comparable to what is caused by the punctures of Cynips 

 and other gall-producing insects. 



Podisoma fuscum is found in Britain, and some other parts of 

 Europe on the savin (Juniperus Sabince). Tulasne collected it in 

 Provence on Pinus halepensis and Juniperus Oxycedrus. In the 

 United States it occurs sometimes on Juniperus Virginiana, but 

 does not appear to have been detected until sent to us this year by 

 Mr. Peck. Of its identity there can be no doubt. It causes the 

 swellings known as Cedar Balls, in the same maimer as its ally, 

 Podisoma macropus, but, both externally and internally, gives 

 evidence of being the species to which we have referred it. This 

 species may be known from P. juniperi by its general form, dark 

 colour, darker protospores, and teleutospores, and by the greatly 

 different form of the protospores. The teleutospores are nearly 

 of the same for-tn in both species. 



Podia oma macropus J is a North American species, never having 

 been detected in the Old World. It is the most common species 

 on the cedar (Juniperus Virginiana), which is therefore the un- 

 fortunate host that supports in the New World not only its own 

 special parasite, but also the Gymnosporangium, and both the other 

 species of Podisoma. This is evidently the Podisoma Juniperi- 

 Virg/niance, of Fries. Dr. Wyman§ has well characterized it as 

 growing on the branches, and also on the slender twigs which form 

 abnormal tufts on the cedar. On the branches excrescences are 

 formed which resemble galls, and these are called " Cedar Apples." 

 The surface is "generally marked with small depressions, from 

 which at certain periods there projects a small point varying in 

 length ; this process consists entirely of fungi, which are developed 



* Corda, Icon. Fung., vol. iii., p. 36. 



t Rabenhorst, Deutschl Flora, vol. i., p. 29. 



X Schweintz in " American Philosophical Transactions." New Series, vol. iv. 

 (1834), p. 307. No. 3096. 



§ J. Wyman, in '"Hooker's London Journal of Botany," vol. iv. (1845), 

 pp. 315-319, t. xii., f. 6. 



