72 COMPENDIUM OF GENERAL BOTANY. 



BARY'S (1877) l attempt to introduce a scientific terminology, which 

 HABERLANDT(1879) 2 strictly adhered to and embodied in his writ- 

 ings. At the present time there is no author in Germany prepared 

 to offer a generally acceptable terminology of tissues which could 

 be introduced in a manual of botany. The best means of making 

 one's self understood and of offering something useful to the begin- 

 ner in scientific botany is, according to my opinion, the following: 

 One must revert to the expressions which had their origin, in part, 

 with the older anatomy, and which designated definite cell-forms, 

 such as " vessels," " tracheids," " wood-parenchyma," tl medullary 

 rays," " thick-walled bast," " libriform-tissue," and " sieve-tubes " 

 as "cambiform" and "conducting cells" ; and further, it must be 

 established that there are (1) water-conducting elements, namely 

 vessels and tracheides ; (2) mechanical elements : bast-cells and 

 bastlike cells ; the latter when occurring within the cambium-ring 

 were already named " libriform " by earlier anatomists ; (3) ele- 

 ments which conduct carbohydrates (or physiologically similar sub- 

 stances) : wood-parenchyma with medullary rays; (4) albumen-con- 

 ducting elements : sieve-tubes with cambiform and conducting cells. 



These cell-forms (1-4) designated by definite names must be 

 clearly distinguished. We shall now briefly consider their anatom- 

 ical characteristics, which are already partly known from what has 

 gone before. 



In the mature state the vessels and tracheids are dead elements, 

 since they are without a primordial utricle. Vessels are generally 

 tubes resulting from cell-rows whose transverse walls have either 

 entirely or partially disappeared (reabsorbed), leaving ridges, or 

 rings, and whose longitudinal walls are strengthened by various 

 thickenings (compare cell-structure). Tracheids are closed prosen- 

 chymatous dead cells whose walls resemble those of the vessels. 

 There are " spiral," " reticular," ll scalariform," and " porous" tra- 

 cheids. Porous tracheids are particularly numerous ; they usually 

 have the form of typical prosenchyrna-cells, and may be named 

 fibrous tracheids as distinguished from the large-celled vessel-like 

 tracheids. We have already learned to know the typical mechanical 

 cells (Fig. 38) as thick-walled prosencby ma-fibres with delicate linear 

 pores which usually extend diagonally. While the large-celled 



1 Comparative Anatomy, p. 330, et seq. 

 2 Entwickelungsgeschickte des mechauischen Gewebesystems. 



