42 



Report was made upon a depauperate form of Bideus ceruna L., found 

 on the Wabash banks. 



Among the forest trees special notes were made upon distribution, size, 

 &c, of Celtis ruimssippirnsis Bosc; Carya olivxformis Nutt; Quercus lyrata 

 Walt.; Diospyros virginiana L., and Taxodium dhtichum Richard. 



Epidermis and spines of cactaceje. By E. B. luxi:. 



Before entering upon the revision of Cactacea' now in preparation un- 

 der President Coulter's direction at Indiana University, a series of inves- 

 tigations on the minute structure of such material as was then available 

 was made during the winter and spring terms of 1892. It was our pur- 

 pose not only to learn of the general morphological nature of the family, 

 but also to discover, if possible, any new diagnostic characters that might 

 be of service in the revision. I have therefore selected for presentation 

 only such peculiarities of structure as may prove of most use in specific 

 determination. 



Though nearly a year had passed since the collection of the material, it 

 was still green and in good condition, with tissues fresh and distended as 

 in growing specimens— thus making it highly favorable for study. Sixty- 

 five species were examined, represented generically in the following 

 proportions: ^lamillaria, 17; Echinocactus, lfi ; Cereus, I'l : Opuntia, 11. 



The most striking feature at first sight is the entire absence of true fo- 

 liage. Naturally, my first inquiry was for some specialized organ or region 

 which should represent, and perform the functions of the missing foliage. 

 The even distribution of stomata and chlorophyll over the entire surface 

 declares the plant itself to be one gigantic and curious leaf so far as func- 

 tion is concerned. However, regarding leaves as devices for increasing 

 surface exposure (expansion of surface formed by the ultimate branch- 

 ing of the fibro- vascular system), I was led to look to the wart-like mam- 

 illse of the genus Mamillaria, and to the tubercles and ribs of Cereus, 

 Echinocactus and certain species of Opuntia as the homologues of leaves. 

 Transverse sections of the tubercles of Mamillaria macromeris show fibro- 

 vascular branching similar to that of the leaf,— the chief difference lying 

 in the cylindrical nature of the one as distinct from the flat surface < if 

 the other. This conclusion is verified by the position of the flowers and 

 branches, which in nearly all cases proceed from the axils of the tuber- 

 cles and mamillse. The genus Opuntia alone is described as having leaves. 



