278 Alexander IV. Evans, 



between the middle portion and the margin is distinctly evident. 

 There is no definite border, however, as in M. Berteroana. 

 Sometimes, in wet situations, the appendages remain very small, 

 although even under these circumstances the marginal teeth form 

 a conspicuous feature. The more sharply pointed apices, the 

 larger and more irregular teeth, the larger marginal cells and the 

 lack of cells containing oil-bodies will at once distinguish the 

 appendages of M. domingensis from those of M. polymorpha. 



According to the original description of M. domingensis the 

 female receptacle is semicircular and ten-lobed to the middle, 

 the lobes being dilated and emarginate-crenate at the apex. The 

 Synopsis gives the number of lobes as seven to ten, while Stephani 

 states that nine lobes are present. The original description of 

 ]\I. infiexa assigns nine to eleven lobes to the receptacle, while 

 Sullivant gives seven to nine as the number of lobes in M. 

 disjuncta; here again Stephani places the number of lobes defi- 

 nitely at nine, and gives the same number for M. Elliottii. In 

 M. caracensis, however, he states that only five or six lobes are 

 present. As a matter of fact the receptacles are exceedingly 

 variable and it is not easy to decide what the typical or normal 

 number of lobes really is. In the material from the mainland 

 seven is perhaps the usual number but five lobes often occur 

 and more than seven have been observed in several instances. In 

 the West Indian material nine lobes are present more frequently, 

 but seven or even only five lobes are not unusual. Sometimes the 

 lobes seem to be subdivided, so that it is not always easy to count 

 them except by means of the involucres which alternate with them. 

 The lobes vary not only in number but in thickness. In some 

 cases they are very thin and flat, in other cases thicker and 

 convex. When the lobes are fleshy the center of the disc some- 

 times shows a low swelling, but it is usually plane, and the recep- 

 tacle never shows the conspicuous median protuberance and 

 radiating ridges which are so characteristic of M. paleacea. 



The study of the involucre is beset with considerable difficulty 

 on account of its extreme delicacy. This has apparently been 

 the cause of considerable confusion in the published descrip- 

 tions. In M. domingensis, for example, the involucre is said to 

 be laciniate-ciliate or shortly fimbriate; in M. infiexa, laciniate; 

 in M. disjuncta, sparingly dentate or subentire ; in M. caracensis, 

 shortly fimbriate. Fig. 12, E-J, brings out the range of variation 



