1894. ] Papers Read Before Section G, A. A.A. S. 371 
even a variety, as it is found growing on the tops of numer- 
ous trees of the species. A summary of comparisons of A. 
barbatum and A. barbatum nigrum was given. It was shown 
that color of branches and stems, shape of top, number of 
leaf lobes, depth of sinus, leaf-texture, could none of them 
be used as diagnostic characters. Intermediate forms be- 
tween the species and variety were also noted and the author 
inclined to the conclusion that the varietal rank of A. barba- 
tum nigrum is reasonably established. 
COULTER, JOHN M.: Some affinities among Cactace@.—A 
study of our species of Cactus (Mamillaria), Anhalonium, and 
Lophophora has suggested certain lines of genetic affinity, 
indicated by the relative position and structure of the tuber- 
cles, spines and flowers. In the discussion the two subgenera 
of Cactus (Eumamillaria and Coryphantha) were considered 
Separately. Eumamillaria is characterized by its grooveless 
tubercle, which bears at its summit the spine-bearing areola, 
and in its axil the flower-bearing areola. Coryphantha shows 
the same relative position of the two areola but they are 
connected by a deep woolly groove running down the upper 
face of the tubercle; in fact, the two areola seem to be but 
expansions of the groove at its extremities. In Echinocactus 
the two areola become contiguous at the summit of the tuber- 
cle. The relation between Echinocactus and Coryphantha 18 
made evident by intermediate forms, in which the groove 
gradually shortens, making the flower areola more and more 
extra-axillary, so that it gradually ascends the tubercle, until 
reaching its summit and becoming contiguous with the spini- 
ferous areola, the resulting form is an Echinocactus. Whether 
the groove has gradually shortened or lengthened is not clear, 
but the indications are that the Echinocactus condition has 
given rise to Coryphantha, and that, in turn, by the closing 
snes groove, to Eumamillaria. Related to these forms are 
ar aberrant genera, now regarded as such, but frequently 
relapses referred to Cactus (Mamillaria) and Echinocestis 
a faeces and Lophophora. The real anageie i 
Poth radee genera are indicated upon an examination 0 i nial 
ot Con The very young tubercles of Anhalonium are ok 
the Pol Seaalie such as those of Cactus macromeris, Wi 
ing seas, areola extra-axillary, the woolly pokes 
tte alf way down the tubercle. In later dev P Bs 
€r, the upper and lower portions of the tubercie 
