174
J. HESLOP-HARRISON
Table I, part of a comparative table given by Clausen and Hiesey, gives
the essential information about distribution, ecology, periodicity and
internal variation for the four subspecies.
The accounts given of the internal variation of the subspecies indicate
that each is genecologically differentiated at a lower level. The pattern
of this differentiation is related to local climate and microclimate as
determined by aspect and altitude, and also to edaphic features. Subsp.
typica is quite evidently extremely heterogeneous ; according to Clausen
and Hiesey, .“Individuals within each local population differ in minor
but distinguishable morphological and physiological characters. Neighbouring populations differ statisticaIly in their average biotype composition even though they belong to the same ecotype. Populations from
climatically distinct regions are to a greater degree divergent both
morphologically and physiologically and represent ecotypes.” Subsp.
refexa is also recorded as being heterogeneous, but seemingly to a lesser
degree. Two distinct ecotypes are distinguished within it : one, inhabiting low level forest, being winter active and early flowering in cultivation, and the other, from higher level Pinm ponderosa forest,. being
winter dormant and late flowering. Subsp. hanseni, although occupying
only a comparatively small total area, is one of the most variable of the
four occurring in California. It is described by Clausen and Hiesey as
constituting a link between the foothill and high altitude races of the
subsp. refexa and nevadensis. In morphological features and earliness,
“with increasing altitude . . . hanseni tends more and more to resemble
nevadensis.” Moreover, the same trend is present in life form - “The
forms of hanseni are generally hemicryptophytes . . . the hanseni populations from lower altitudes, however, develop short woody crowns
similar to the chamaephytes of refexa, whereas those from higher
altitudes are more rhizomatous, as in nevadensis. ” These observations
certainly seem to show that a system of clines does exist in hanseni, but
later in the same account $he authors appear to deny that this is so.
Subsp. nevadensis, from the highest altitudinal belt, appears to reveal
the narrowest range of variation, but even so, genecological differentiation is present. Two climatic ecoty-pes are described, one alpine and the
other sub-alpine, differing morphologically and in periodicity.
Clausen and Hiesey relate the distinctness of the four central Californian subspecies of P. glandulosa to the sharply differentiated climatic
zones across the transect from the Pacific to the Sierra Nevada. They
remark that north and south of the area investigated in detail the
pattern of zonation becomes obscured; then, “the rather well defined
subspecies found in central California break down into other combinations of characters.” Within the area where the subspecies are well
distinguished, inter-gradation between them is said to be minimal, and
J. HESLOP-HARRISON
Table I, part of a comparative table given by Clausen and Hiesey, gives
the essential information about distribution, ecology, periodicity and
internal variation for the four subspecies.
The accounts given of the internal variation of the subspecies indicate
that each is genecologically differentiated at a lower level. The pattern
of this differentiation is related to local climate and microclimate as
determined by aspect and altitude, and also to edaphic features. Subsp.
typica is quite evidently extremely heterogeneous ; according to Clausen
and Hiesey, .“Individuals within each local population differ in minor
but distinguishable morphological and physiological characters. Neighbouring populations differ statisticaIly in their average biotype composition even though they belong to the same ecotype. Populations from
climatically distinct regions are to a greater degree divergent both
morphologically and physiologically and represent ecotypes.” Subsp.
refexa is also recorded as being heterogeneous, but seemingly to a lesser
degree. Two distinct ecotypes are distinguished within it : one, inhabiting low level forest, being winter active and early flowering in cultivation, and the other, from higher level Pinm ponderosa forest,. being
winter dormant and late flowering. Subsp. hanseni, although occupying
only a comparatively small total area, is one of the most variable of the
four occurring in California. It is described by Clausen and Hiesey as
constituting a link between the foothill and high altitude races of the
subsp. refexa and nevadensis. In morphological features and earliness,
“with increasing altitude . . . hanseni tends more and more to resemble
nevadensis.” Moreover, the same trend is present in life form - “The
forms of hanseni are generally hemicryptophytes . . . the hanseni populations from lower altitudes, however, develop short woody crowns
similar to the chamaephytes of refexa, whereas those from higher
altitudes are more rhizomatous, as in nevadensis. ” These observations
certainly seem to show that a system of clines does exist in hanseni, but
later in the same account $he authors appear to deny that this is so.
Subsp. nevadensis, from the highest altitudinal belt, appears to reveal
the narrowest range of variation, but even so, genecological differentiation is present. Two climatic ecoty-pes are described, one alpine and the
other sub-alpine, differing morphologically and in periodicity.
Clausen and Hiesey relate the distinctness of the four central Californian subspecies of P. glandulosa to the sharply differentiated climatic
zones across the transect from the Pacific to the Sierra Nevada. They
remark that north and south of the area investigated in detail the
pattern of zonation becomes obscured; then, “the rather well defined
subspecies found in central California break down into other combinations of characters.” Within the area where the subspecies are well
distinguished, inter-gradation between them is said to be minimal, and