158 



angular portion ; the „secondary lobe", in the distal axil of the 

 primary lobe. 



Type (b). Bursa bursa-pastoris rhomboidea Las the leaves 

 divided to the mid-rib as in B. bp. Jieteris. The lateral lobes have 

 an incision on the distal niargin 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 blnnt 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. Jieteris 

 and B. bp. rhomboidea. 



Type (d). Bursa bursa-pastoris Simplex, like B. bp. tenuis is 

 scarcely ever divided nearly to tbe 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 I — IV. 



