182 Floristik, Geographie, Horticultur und Systematik etc. 



{Trachynotia juncea Michx.), S.patens caespitosa {S. caespitosn Eaton), 

 Cteniiim arornaticuni {Aegüops aromatica Walt.), TrideMS flava {Poa 

 flava L., Triodea seslerioides Benth.), Melica striata {Avena striata 

 Michx.), Glyceria Torreyana {Poa Torreyaiia Spreng.)^ G. pallida 

 Fernaldii, G. septentrionalis , Broiniis latiglumis (B. ciliatits latiglumis 

 Scribn.)^ B. incanus {B. puvgans incamis Shear), and Elymiis striatiis 

 arkansanus (E. arkansanus Scribn. and Ball). Irelease. 



Holm, Theo., Coninielinaceae. Morphological and anatomical 

 studies of the vegetative organs of some North and Central 

 American species. (Mem. Nat. Acad. of Sc. X. p. 157 — 1^2. 

 f. 1—53. 1906.) 



Seventeen species of the genera Lommelina , Aneilema , Tinantia, 

 Tradescaiitia and Weldenia have been studied. The habitns of these 

 plants is very different even within the same genus. In Coninielina , 

 C. niidiflora is an annual, while the others are perennial; C. hirtella 

 has a horizontally creeping rhizome with slender roots; C. Virginica , 

 on the other hand, has a very short rhizome, but thick, fleshy roots. 

 In Tradescantia , T. niicrantha and T. Floridana show the same habit 

 as ConimeWia , the stems being decumbent and the leaves short and 

 broad. Very different from these are T. pinetoruni with long leaves, 

 erect stems, creeping rhizomes and tuberous roots; in T. Warsse- 

 wicsiana the leaves form a dense rosette at the apex of the short 

 aerial stem, while the inflorescence is borne on a long, naked scape. 

 Characteristic of Weldenia is the profuse development of tuberous 

 roots. The external structure of the aerial and subterranean portions 

 of the shoot is described and figured, including diagrams showing 

 the Position of the leaves. In Commelina and Tina)itia the fore-leaf 

 alternates with the leaf of the mother-shoot, while the succeding 

 leaves are turned 90° to the side of the fore-leaf. In Tradescantia 

 on the other hand, all the leaves are alternate. 



The internal structure of the vegetative organs is discussed and 

 illustrated. The roots represent several t3^pes, for instance: simply 

 nutritive (C. niidiflora , Tinantia , Aneilema and Tradescaiüia Floridana) , 

 nutritive and at the same time contractile (Trad. WarcB. and C hirtella) , 

 nutritive and storage roots {Trad. crassifolia) , and finally contractile 

 and storage roots in Trad. Virgi)iica , C. Virginica etc. All the roots 

 were found to possess an exodermis, which in Weldonia is composed 

 of two layers; stereids occur in a few species of Coninielina and 

 Tradescantia. In Aneilema the cortex collapses, but remains solid in 

 all the others. The pericambium is sometimes interrupted by the 

 proto-hadrome in C. nudiflora , C. Virginica and Trad. rosea. In the 

 roots of Weldenia the number of hadromatic rays is about twenty 

 and there is a broad central pith, while in the other plants the pith 

 is generally very little developed, and the number of hadrome-rays 

 much smaller. In regard to the rhizomes hypodermal Strands of 

 collenchyma were observed in C. hirtella, but not in any of the 

 others; this species has, furthermore, an endodermis besides a closed 

 sheath of stereome. In the stem above ground the collenchyma is 

 always present, and directly beneath the epidermis. An endodermis 

 was found in the species of Commelina and Tinantia, also in Trad. 

 Floridana j but not in the others. A closed sheath of stereome occurs 

 in several of these plants. The mestome-bundles of the stem above 

 ground are collateral and arranged in several concentric bands; in 



