folm —Mollugo verticillata 



Systematische Anatomie der Dicotyledonen.* A brief descrip- 

 tion of the stem is given by Karl Christ, f In speaking of the 

 roots of the Fieoideoe Solereder (1. c.) states that the anomalous 

 structure of the stem generally recurs in the root-system ; 

 however, the stem-structure of our Mollugo is anything but 

 anomalous, and the root-structure is indeed very simple. At the 

 seedling-stage the primary root has a hairy epidermis, and a 

 thinwalled cortex of only two strata. Endodermis is, also, 

 thinwalled, and the pericambiurn consists of a single layer of 

 thinwalled cells ; the stele is diarch with a diametric ray of 

 vessels, and with two strands of leptome. Increase in thick- 

 ness commences early, but only within the stele so long as the 

 individual has not reached the flowering stage. In mature 

 specimens the primary root is a little thicker, but relatively 

 short, and sparingly branched ; epidermis and cortex with part 

 of endodermis are now replaced by several strata of thinwalled 

 cork developed from the pericambiurn, and the stele consists 

 now of a dense mass of collateral mestome-strands. In other 

 words, the structure agrees with that, which is the most common 

 in roots of dicotyledonous plants. 



In passing to describe the stem we might begin with the 

 hypocotyl. This stem-portion shows, also, an early increase in 

 thickness by the formation of pericyclic cork, and by the 

 development of secondary mestome-strands between the pri- 

 mordial, while the individual is a mere seedling bearing only 

 the cotyledons and a minute vegetative shoot. At this stage 

 epidermis is thinwalled, and the cortex is composed of only 

 two layers of very large cells surrounding a typical, thinwalled 

 endodermis. Inside the cork is a continuous band of leptome, 

 and hadrome of wide vessels extending to the center, and with 

 thickwalled parenchyma between these. If we compare this 

 structure with that of the hypocotyl of a mature specimen, we 

 notice no difference except that it contains a little more cork, 

 but even so, all the peripheral tissues from epidermis to endo- 

 dermis are still present. 



In regard to the stem proper, and especially the stretched, 

 prostrate internodes, these exhibit the structure as follows : 

 They are cylindric, glabrous and perfectly smooth, covered 

 with a very thin cuticle ; the outer cell-walls of epidermis are 

 slightly thickened, and the cortex is compact, but consists only 

 of three strata with a little chlorophyll, beside that many of the 

 cells contain styloids of calcium oxalate. There is a distinct 

 endodermis, which contains starch, and pericycle representing 

 a closed sheath of stereome (S in fig. 5) in one to two layers, 



* Stuttgart, 1899, p. 468. 



f Beitrage zur vergleich. Anat. d. Laubstengels der Caryophyllinen. 

 sis, Marburg, 1887. 



The- 



