MORPHOLOGY OF HIGHER PLAXTS. 



405 



the pollen grains to adhere, as in CEnothera. The grains may be 

 smooth or variously sculptured ; in most instances the exine is 

 unevenly developed, leaving thin places through which the pollen 

 tubes protrude in germination; these give the appearance of 



Ftg. 234. A, Crocus (Spanish saflfron) showing two spherical pollen grains, a fragment 

 of stigma with papillae, and fragment of an anther; B, Calendula showing 3 spinose pollen 

 grains and fragment of corolla, the cells of which contain oil-like globules; C, Carthamus 

 (so-called American saffron) showing 2 slightly spinose pollen grains and a fragment of 

 the corolla with brown laticiferous vessels and numerous unicellular hairs. — After Weakley. 



grooves when the grains are dry, and the number of grooves is 

 characteristic for different species ; in most of the Compositae 

 they are three in number ; in the Labiatae there are six, while in 

 Crocus they are wanting (Fig. 234). 



The epidermal cells of the stigma are quite characteristic. 



