Anatomy of Hesperomannia — CARLQUIST 
211 
species. In addition, subepidermal cells in- 
terior to the lateral veins of the lobe may 
become sclerified; such diffuse sclereids were 
found in all the subspecies of H. arborescens 
and H. arbuscula. The extent of these sclereids 
is shown diagrammatically in Figure 4F for 
H. arborescens subsp. Swezeyi , in which they 
were abundant. They were least abundant in 
H. arbuscula subsp. arbuscula , and altogether 
lacking in H. Lydgatei (Fig. 4G). Sclereids of 
this type appear in the young flowers, and 
increase in size until the corolla withers. As 
shown in Figure 5, these sclereids become 
impacted against each other, forming blunted 
ends and distorted shapes. Because of the 
presence of such sclereids, median veins in 
corolla lobes can be detected with certainty 
only in cleared preparations. Although scler- 
eids of this nature have never been reported 
in the Compositae before, they have been 
found by the writer in a number of Mutisieae. 
EVOLUTION WITHIN THE GENUS 
Characters of gross morphology alone give 
few suggestions concerning presumed evolu- 
tionary advancement within Hesperomannia. 
One feature which deserves mention is the 
tendency toward aggregation of heads. In 
most Mutisieae, particularly putatively prim- 
itive genera, the heads are solitary and ter- 
minal. In Hesperomannia , they may be solitary, 
but are more frequently in clusters of 2 to 10. 
Where fewer peduncles are present, they are 
borne coordinately at the end of an axis. 
Where more numerous peduncles form a 
cluster, some peduncles may branch from 
others. If more than one head is present, no 
leaves or bracts subtend the additional heads. 
In view of the fact that clusters of heads are 
present in all of the taxa except H. arborescens 
subsp. Bushiana , which would appear to be 
derived on other grounds, such clusters may 
Fig. 5. Portion of cleared corolla-lobe of Hespero- 
mannia arborescens subsp. Swezeyi ( Judd 1244), X 175. 
Margin of lobe at right; inward from the margin may 
be seen the lateral vein, a glandular hair (out of focus), 
and a number of subepidermal sclereids, left. 
have been primitively present in Hesperoman- 
nia , despite the solitary condition elsewhere 
in the Mutisieae. 
Anatomical characters seem to offer more 
reliable criteria of primitiveness, though few 
features can be cited in this regard. The 
caducous hairs on herbage and peduncles may 
be interpreted in this connection. One would 
expect the development of mature trichomes 
to be more primitive than the condition where 
they are lost at an early stage. In this case, 
H. arbuscula shows the most primitive ex- 
pression of this character. Hesperomannia Lyd- 
gatei shows the most advanced condition, 
-4-Fig. 4. A, B, transections of peduncle near base, X 30. A, Hesperomannia arborescens subsp. Bushiana (Degener 
11927a ); B, H. Lydgatei {Forbes 190K ). C-E, transections of involucral bracts, midway along length of bract, X 21. 
C, H. arborescens subsp. Swezeyi {Judd 1244), outer bract; D, H. arborescens subsp. Bushiana {Degener 11927a), 
inner bract; E, H. Lydgatei {Forbes 190K), outer bract. F, G, corolla lobes, X 15. F . H. arborescens subsp. Swezeyi 
{ Judd 1244); G, H. Lydgatei {Forbes 190K). Outlines and veins shown in black, sclerenchyma shaded. 
