253 
Glands of the Plumb agi neae. 
secreting organs, the chalk-secreting faculty being afterwards 
acquired ? One is inclined to answer this in the affirmative, 
for the alternative, viz. that the chalk-secreting function was 
the original, does not seem tenable, seeing that it implies 
that the necessity for protection by chalk-scales existed in 
all or in the great majority of the members of the family. 
With respect to the purpose subserved by the mucilage, 
extreme cases here also demonstrate clearly enough that 
protection is effected by it. In Statice rosea> as already 
remarked, it coats portions of the leaves in drought with a 
thin brittle film, and when the atmosphere is humid it swells 
up in the axils of this species, and of S. fruticans , and 
envelops the buds and tender bases of the leaves. Un- 
questionably, its hygroscopic power will be of service in 
attracting, storing and economising atmospheric moisture. But 
difficulties meet us when we try to explain its presence 
in the leaf-axils of plants ( Armenia , Statice) which live 
in marshy stations with the bases of the leaves often in 
contact with the humid soil. Extended research with living 
plants in their native haunts is called for, before a full and 
comparative account of the physiology of the glands can be 
given. 
The possession of Mettenian glands is most probably a 
universal feature in the cotyledons of the family. The 
absence of the mucilage-glands from the cotyledons of the 
Plumbago examined points to the likelihood that only certain 
genera possess them in that situation. One is apt to imagine 
that they are likely to occur there in genera possessing them 
conspicuously in the adult ; in Aegialitis, for example, and, 
conversely, not in Acant/iolimon. Maury has been more 
fortunate than I hitherto in being able to get good seed of 
the latter. Although he does not mention any special 
glands in the cotyledons of this genus, they may nevertheless 
be there, seeing that he makes no note of them in Armeria 
and Statice , where they do occur distinctly. If they are 
present the question arises, Did Acantholimons formerly more 
closely resemble Armerias and herbaceous Statices in habit 
