40 _ MISSOURI BOTANICAL GARDEN, 
typically represented by A. aurea; and a form with dagger- 
like, heavy-prickled leaves, also confined to the lower half 
of the peninsula, of which A. Datylio is representative. 
These groups are fairly consistent in flowers and fruit except 
that a number of plants that resemble A. Shawii somewhat 
in growth prove on these characters to be more closely related 
to the very different looking A. deserti, around which cluster 
the largest number of forms. In the synopsis which fol- 
lows, these groups have been made the basis of classifica- 
tion. 
So far as is now known, these groups, like their component 
species, are essentially endemic. The first, Umbelliflorae, is 
most closely allied to the boreal set of species of which 
A Parryi is a well-known representative. The second, Deserti- 
colae, centers about A. deserti, which in its typical form 
occurs in the desert shortly north of the boundary; but the 
occurrence of two species, not placeable elsewhere, on is- 
lands that clearly belong to the mainland and not the penin- 
sula, gives reason to suppose that this group may be found 
to have mainland representatives not yet made known. The 
third, Campaniflorae, though notably different, can be com- 
pared with nothing as closely as with A. Palmeri of the 
Arizona region, which possesses an undescribed equivalent 
in Durango. The fourth, Datyliones, is of the stock to which 
the Sisalanae of Yucatan and the Tequilanae of southern 
and western Mexico belong, and apparently more closely re- 
lated to the former. The first three groups, which comprise 
nearly all of the species known for Lower California, thus 
give indication in their relationships of the probability, 
pointed by geographic considerations, of their entry around 
rather than across the Gulf; but this conclusion is not evident 
in case of the Datyliones, and much less evident for the Cam- 
paniflorae than for the first two groups. 
It is interesting that Agave, like Nolina, Yucca, Fouquie- 
ria, ete., seems to have passed into Lower California from 
the northeast without entering California except in its south- 
ernmost desert part, while close allies of the first (Manfreda, 
widely distributed through Mexico and sparingly represented 
