IS4 



DICOTYLEDONS 



lobed and divided into four chambers, each containing one 

 ovule; style attached between the bases of the four lobes of 

 the ovary. Fruit a schizocarp of from one to four nutlets. 



Typp : WHITE DEAD NETTLE (Lamium album). 



Vegetative characters. — Perennial herb with a four-sided 

 stem. Leaves opposite, exstipulate, with scalloped or saw-like 

 margins. Inflorescence. — Each infioresence which stands in 

 the axil of a leaf is a dichasium with a terminal flower and 



two lateral one - branched 

 cymes (monochasia). Flower 

 (fig. 191) median -zygomor- 

 phic, $ , cyclic, hypogynous. 

 Sepals (ex) five, combined. 

 Petals {pp, Ip, ap) five, com- 

 bined to form a two -lipped 

 corolla. In order to under- 

 stand that there are five petals 

 represented in the corolla, it 

 is necessary first to remember 

 that the petals alternate with 

 the sepals. It will then be 

 seen that the three-lobed lower 

 lip represents one anterior 

 petal {ap) and two lateral 

 petals {Ip) alternating with 

 two anterior sepals. In like 

 manner the upper lip of the 

 corolla represents two pos- 

 terior petals (//), one on each 

 side of the median posterior sepal (see diagram fig. 192). The 

 slight notch in the apex of the upper lip also denotes that the 

 latter represents two closely joined petals. A ring of hairs {h) 

 lines a zone of the corolla-tube. Stamens four, the two anterior 

 stamens having longer filaments than the other pair, inserted 

 on the corolla. In order to understand the androecium we 

 must again remember that the stamens should alternate with 

 the petals. There should, therefore, be a median posterior 

 stamen, but no such stamen is present. We therefore con- 

 clude that the median posterior stamen has been suppressed : 



Fig. igi. — Vertical section of iiower of 

 Dead Nettle. 



