ANOMALOUS THICKENING IN DICOTYLEDONS AND GYMNOSPERMS. 59I 



Amarantus retroflexus, Celosia argentea, Alternanthera Verschaffeltii (Atnarantacese) ; 

 of Chenopodium album, Atriplex patula, and Salicornia herbacea. 



Between these two chief modes or types the following are intermediate. 



3. In the root of Mirabilis the phenomena of secondary thickening are the same 

 as in I. as far as the appearance of the first renewed zone of cambium. This then 

 remains permanently extrafascicular and active according to mode 2. The same 

 behaviour appears to occur in the roots of Oxybaphus ; those of other Nyctagineas 

 have not been investigated. 



7C4. The stems of many Chenopodiacese, as Ch. hybridum, Ch. murale, connect 

 types I and 2, since a normal cambium and a normal secondary thickening appears 

 as in I in their primary ring of bundles ; this however soon stops, and the further 

 growth in thickness is continued, according to mode 2, by a new extrafascicular zone 

 of cambium, which appears outside the primary masses of phloem. Blitum virgatum, 

 Gomphrena decumbens and globosa, and Froelichia gracilis behave in this way; 

 their slightly thickened herbaceous stems show for a long time only a quite normal 

 thickening, the bundles situated outside the ring of bast appear in small numbers, 

 or often not at all. 



The relation between i and 4 being very close, it is impossible to distinguish 

 in the old stem whether the first stages of thickening proceed according to the one 

 or the other type. Therefore in the case of Atriplex Halimus, Obione sp., Salsola 

 kali, Arthrocnemum fruticosum, Haloxylon ammodendron, Caroxylon arbuscula, 

 Alternanthera spinosa, jiErva javanica, Achyranthes aspera, Pupalia Schimperiana, 

 and according to Regnault's statements in the Tetragoniese Galenia, Trianthema, 

 and Tetra,gonella, of which the first stages were not investigated, it can only be said 

 that they certainly belong to one of the two types. 



This is the proper place to insert a remark upon the terms which have been, and ought 

 to be employed. According to the terminology which is usual, and has been adopted in 

 the preceding chapters, each thickening zone with normal orientation and structure is to 

 be denominated, even in the cases before us, respectively cambium, ivood, bast, &c., and 

 there is no difficulty in applying these terms to successively renewed and arrested annular 

 zones. But in those cases (2) in which the orientation of the meristematic layer, which 

 brings about the secondary thickening, is from the first other than normal, the adoption 

 of the terminology used in other cases may be questioned. Even if intermediate forms 

 were not present, it is suitable in all cases to call the initial layer of each secondary 

 thickening here also generally cambium, especially as — leaving out of account special 

 differences which still remain to be investigated — this layer always possesses in itself the 

 other fundamental properties of normally arranged cambium. Since a special name is 

 desired for the special orientation indicated under 2, the term extrafascicular has been 

 chosen for such cambium as appears outside the primary ring of bundles. Starttng from 

 the above reflections we must consistently apply the term nvood in the cases of extra- 

 fascicular cambium also to the secondary thickening, whenever it appears on the inner 

 side of the cambium, and in centrifugal succession, and the term bast to that which 

 appears centripetally on the outside. The bast differs here as in Strychnos from normal 

 bast in its structure, as does the wood also, reminding one of the phenomena described in 

 Strychnos and Dicella. Link calls this wood lignum hybridum, bastard-wood ; but it 

 may be more satisfactory to give up the use of this remarkable name, which was accepted 

 even by Sanio, and to describe precisely in each instance the real state of the case, since 

 . it is subject to such indefinite variation according to the individual instance. 



