1912] JONES— DIANTHERA 23 



D. pedoralis Murr., and D. sessilis Gray, I was unable to obtain 



* 



any of these species for comparison, I did obtain seeds, however, 

 of the fairly closely related Justicia ventricosa. A few of these 

 germinated, and I was able to study a few of the seedling stages. 

 The germination is similar to that described for Dianthera ameri- 

 cana. Likewise are the first three stages. After that, the 

 interfascicular cambium masks the primary structure. 



Comparing this then with Dianthera americana, we find that 

 they are at first exactly the same. The first point of difference is 

 the failure of the interfascicular cambium to appear. This leaves 

 the bundles separate, around which the endodermis turns in and 

 surrounds, instead of remaining as a complete ring, as in Justicia. 



In the mature plant, we find that the first two apical nodes of 

 Dianthera americana are similar to other acanthaceous plants 

 {Justicia, Fittonia, etc.). In the latter, the traces of the first pair 

 of leaves pass down to a ring of vascular tissue. Below this node 

 there are two arcs of tissue, each of which is evidently of three 

 parts, showing three widely separated protoxylems. This inter- 

 node, therefore, has a structure exactly like that of a young inter- 

 node of the inflorescence axis of Dianthera americana. At the next 

 node the opposite leaf traces enter between the two arcs. Below 

 this node the original structure cannot well be made out, owing to 

 secondary thickening. 



It is evident that the seedling and the inflorescence axis of 

 Dianthera americana show the primitive condition of the group, 

 and that the formation of endodermal sheaths around each of the 

 separate bundles, that is, the condition of astely, is a secondary 

 condition, found only in a part of the species of Dianthera (accord- 

 ing to Holm, D. crassifolia Chapm. and D. lanceolata Small, are 

 also"polystelic"). 



Although astely apparently has not been previously described 

 as occurring in the Acanthaceae, yet many other vascular abnor- 



The interxvlarv phloem of Thunbereia and 



oem (Thunbereia. Hex 



malities are known. The interxylary 



others is well known. Intraxylary ph 



ins, Barleria, etc.), medullary phloem (petiole of Acanthus moll 



and even medullary bundles (Acanthus spinosus, etc.), have i 



been described. It is thus seen that the family shows irregul 



ties of vascular structure. 



