10 THE JOURNAL OF BOTANY 



has shown that they possess from twelve to eighteen longitudinal 

 ridges. In the specimen here described and figured (fig. 7), quite 

 apart from the deformity in the shape of the cell, the chloroplasts 

 were of a very extraordinary character. Each one was a continuous 

 parietal mass, w4th a plate-like extension across the median part of 

 the cell, and therefore it formed the walls of a closed chamber 

 containing a large sap-vacuole. In it were numerous scattered 

 pyrenoids. No such chloroplasts have been previously observed 

 in any species of Closteriuvi, not even in a monstrosity. The 

 nucleus was in its normal place and it contained three nucleoli. 

 This monstrosity must be regarded as an involution form. 



Various involution forms of Clostermm moniliferum (Bory) 

 Ehrenb., have been recorded by Andreesen," as oc3urring in 

 artificial cultures, although his monstrosities were more particu- 

 larly plasmolysis-forms. The production of such forms is, how- 

 ever, common knowledge to those who have attempted cultures of 

 Desmids under unnatural conditions. All Andreesen's mon- 

 strosities appear to have been pathological, and none showed any 

 change in the nature of the chloroplast such as is here described 

 for the abnormal form of Closterium Ehrenhergii. 



NOTES ON SOEBUS. 



By the Eev. E. S. Marshall, M.A., F.L.S. 



Dr. Hedll'nd, with whom the Eev. Augustin Ley had a 

 considerable amount of correspondence, has kindly sent me two 

 papers on Sorbiis which deal with several plants found in Britain,. 

 and are therefore of interest to our botanists. Sorhiis, though- 

 included under Pynis in our lists and fioras, is spoken of by 

 Fries (Summa Yeg. Scand., p. 173) as '' naturalissimi hujus- 

 generis," and is retained ni Ny man's Conspectus. It is difficult' 

 to see why this group should be ranged with the apples and pears,, 

 in view of their marked difference in flowers, fruit, and foliage. 



By " homozygotic " and " heterozygotic " — terms not to be^ 

 found in Dr. Daydon Jackson's Glossary — the author appears to 

 mean plants derived from the same or from different groups ; 

 S. Aria x S. Aucuparia being quoted as an instance of a " planta- 

 heterozygotica." 



I. De Sorbo arranensi Hedl. et affinibus homozygoticis 



Norvegise. Auctore T. Hedlund. Eeprinted from Ove 



Dalil: Botaniske Undersokelser i Helgeland. II. (Yiden- 



skappsel-skapets Skrifter. I. M.-N. Kl. 1914. No. 4). 



Pp. 181-4. 



A full description is given of S. arranensis, for which are 



quoted, as synonyms: — " Pyrus scandica Boswell (Syme), on the 



forms of P. aria, in Eep. Cur. Bot. Exch. Club, 1874-5: Journ. of 



Bot. xiii., p. 284 (1875). Sorbus arranensis Hedlund, Monogr. d. 



* A. Andreesen, Beitrcicje zur Kenntnis dcr Physiologie der Desinidiaceen, 

 Jena (CJustav Fischer), 1909. 



