132 The Botanical Gazette. [April, 
these days. As to their morphology most systematists have 
given it some, though usually it has been scanty attention. 
De Candolle appears to have begun the attempt to determine 
the homologies of spine and tubercle and the other riddles of 
the group; various others, including Kauffmann, Vochting, 
Schumann and Wetterwald, and above all Goebel, have de- 
bated point after point, and gradually won the truth. Finally 
I must be permitted to mention my own studies which in 
ground well prepared by my predecessors were made produc- 
tive under the guidance of my teacher Goebel. It remains 
to mention the sources of our knowledge of their biology, 
and here we have but a single source to refer to, the ground- 
work for all future studies of this character, Goebel’s discus- 
sion of their form, protection, and other conditions in his 
‘*Pflanzenbiologische Schilderungen.” 
So much for the characters of this attractive family and 
the pioneers in its study. What now remains for other ex- 
plorers? 
There is neejted first and most important of all, an exact 
investigation into the meteorological and biological conditions 
under which the Cactacee live. An all the year round study 
of the amount and time of rainfall, dew-formation, dryness of 
the air, winds, extremes and means of day and night and sea- 
sonal temperature,7 intensity and amount of light, the kinds 
and habits of enemies and of cross-pollinating and disseminat- 
ing friends, the exact situations in which they grow and the 
nature of the soil, all these must be known about any given 
district before we can more than guess at the ‘‘adaptations” in 
the Cactacez which inhabit it. Excepting for some inci- 
dental study by Goebel in Venezuela and the work of Stahl in 
Mexico last summer, the results of which we have yet to 
learn, no trained biologist has worked upon them in the field. 
Taking first the simpler problems, there are several 1” 
which additional evidence is to be expected. It has beet 
clearly shown that the spines of the Cactacee are metamor- 
phosed leaves, and not ‘‘emergences” as some have claimed. 
The evidence is drawn from the occurrence of normal trans!- 
tional structures which are formed by the axillary vegetative 
points as they begin to sprout into branches, i. e., after they 
Dieieee 
™The only data of this kind are those given by Coville (Contrib. Nat. Herb. 
4: 33-35. 1894), and these are scanty and for only one locality. 
