76 Mr. J. ]\liers on the Tribe Colletiese, and on 



VIII. — On the Tribe Colletiese, ivith some Observations on the 

 Structure of the Seed in the Family of the Rhamnacese. By 

 John Miers, F.R.S., F.L.S. &c. 



This tribe differs from others of the Rhamnacece in having always 

 opposite branchlets usually terminating in acute spines, while 

 in most Rharanaceous genera they are alternate ; for, though 

 they sometimes approximate in pairs, they are never exactly 

 opposite : the same may be said of then" leaves. The Colletiece 

 also differ in the position of their petals and stamens, their in- 

 sertion being always perigynous upon the tube of the calyx at 

 some distance from the hypogynous disk, which in Colletia 

 assumes a perigynous form : in this respect we meet with only 

 one exception, in Adolphia, where, owing to the extreme short- 

 ness of the calycine tube, their point of attachment is drawn 

 close to the disk ; but, although thus brought into proximity, 

 thev are not actually inserted upon its margin, as they are ge- 

 nei'ally in the RhamnecE. In the tribe Gouaniece, so different in 

 most other respects, the insertion of the petals and stamens is 

 like that of the Colletieee. The stamens are placed opposite to 

 as many scale-like petals in all the RJiamnacece ; they are gene- 

 rally concealed and hooded by them in the Colletiea;, and are 

 inserted upon their claws, between the lobes of the calycine 

 border ; the petals are, however, sometimes wanting, and in a 

 single apctalous species the insertion of the stamens is below 

 the middle of the tube. The Colletiea, besides, are generally 

 distinguishable at a glance by their peculiar habit : the branch- 

 lets, half abortive, often assume the form of spines, which are 

 either quite bare, or they are foliiferous, or else they become 

 more elongated, bearing both leaves and flowers, but sometimes 

 they are destitute of both, with a broom-like appearance ; the 

 leaves, when present, are always small and opposite, oi', by the 

 approximation of the axils, almost fasciculated, and are either 

 entire or denticulated, and sometimes are reduced to almost 

 obsolete proportions. Most of the species at present known are 

 natives of South America ; there arc a few in Mexico, one from 

 the Galapagos, one from the island of Juan Fernandez, one from 

 Australia and Tasmania, and another from New Zealand. 

 There has hitherto been much confusion among the genera, the 

 characters of many of them being still undefined : thus Trevoa 

 and Talguenea, which I proposed above thirty years ago, have 

 been confounded together by most botanists. My observations, 

 I hope, will enable me to define the characters and limits of 

 these as well as the other genera of the tribe. 



When Jussieu published his 'Genera Plantarum ' (in 1789), 

 the only genus then known of the present tribe was Colletia ; it 



