NOTES ON THE ANATOMY OF OPUNTIA LINDHEIMERI 



ENGELM. 



FREDERICK A. WOLF 



Agricultural Experiment Station, Auburn, Alabama 



Since the publication of Schleiden's 1 Anatomie der Cacteen, 

 numerous workers have contributed to our knowledge of the 

 histology of cacti. Any one who has studied this group of plants 

 is well aware of the fact that there is yet much to be understood 

 concerning them. It is evident, upon further study, that in a 

 recent paper, 2 I did not record correctly the structure of certain 

 tissues and consequently am in error in regard to their nature. 

 It is, therefore, the purpose of this paper to rectify these errors 

 and to contribute other additional observations. 



Among these plants there would seem to be no doubt that the 

 formation of cork, one of the most common phenomena which is 

 known to occur, is of pathological origin. 3 In order to better 

 understand the changes which take place in cork formation in 

 Opuntia lindheimeri, it is necessary to indicate the arrangement 

 of tissues in a normal plant. As shown in figure 3, the outer epi- 

 dermal wall is strongly cuticularized. The hypodermal layer, 

 subjacent to the epidermis, contains large calcium oxalate crystals. 

 Between the hypoderma and the chlorenchyma is a layer of col- 

 lenchyma 3 to 5 cells thick, the walls of which are stratified and 

 coarsely porous. As Schleiden has shown, cork formation begins 



1 Schleiden, M. J., Beitrage zur Anatomie der Cacteen. Memoires de l'Acad- 

 emie Imperiale de Sciences de St. Petersburg. Ser. 6, T. 4: 335-380, pis. 1-10 

 (1839), 1841. 



2 Wolf, F. A., Some fungous diseases of the prickly pear, Opuntia lindheimeri 

 Engelm. Ann. Myc. 10: 8-134, pis. 1-3 + figs. 8, 1912. 



3 Hillhouse (vide Strasburger and Hillhouse, Practical Botany, p. 188, 1908) 

 suggests that it seems probable that all cork has phylogenetically a pathological 

 origin. 



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