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angular portion, tlie „secondarj lobe", in the distal axil of the 
primary lobe. 
Type (b). Bursa hursa-pastoris rhomhoidea has the leaves 
divided to the mid-rib as in B. bp. heteris. The lateral lobes have 
an incision on the distal margin setting off the secondary lobe 
from an unelongated primary lobe. There is usually a corre- 
sponding incision on the proximal margin of the primary lobe. 
In the best developed specimens these incisions set off a small 
terminal portion of each lateral lobe, which is rather blunt or 
angular at the apex, being generally of rhomboidal form. Less 
perfectly developed specimens have the incisions very shallow or 
nearly wanting, but retain the characteristic deep sinuses extending 
to the mid-rib. 
Type (c). Bursa bursa-pastoris tenuis differs from both (a) 
and (b) in that the sinuses do not usually reach the mid-rib. 
The terminal lobe is not separated from the nearest lateral lobes 
by deep, clean-cut sinuses, these more distal sinuses being rela- 
tively shallow, so that one can with but scant propriety speak 
of the terminal lobe as a definite morphological structure. All the 
lateral lobes tend to be elongated and sharp, and no incisions 
are present to set off a secondary lobe, though in particularly 
vigorous specimens there may be a slight expansion of leaf-tissue 
in the region occupied by the secondary lobe in B. bp. heteris 
and B. bp. rhomboidea. 
Type (d). Bursa bursa-pastoris simplex, like B. bp. tenuis is 
scarcely ever divided nearly to the mid-rib, and the lateral lobes 
are mostly obtuse, sometimes more or less acute, but never long 
and attenuated. No secondary lobing appears except occasionally 
a slight denticulation on the margins. 
These descriptions refer to the characters of the climax- 
leaves in well-grown specimens, as all of these types have juve- 
nile leaves entirely unlobed and indistinguishable from the juve- 
nile leaves of the other forms, and the late rosette-leaves and 
stem-leaves likewise generally lack distinctive features. Under 
poor cultural conditions plants frequently complete their development, 
flower, and ripen their seeds, without exhibiting any but these 
juvenile and senescent characters. The complete procession of 
leaf-forms in typical specimens of the four described biotypes are 
shown in the plates 1— IV. 
