AXIS FLOWERS 305 



strongly 2- lipped, and its attached stamens are reduced 

 to two, the other three having disappeared. The 

 bicarpellary pistil contains two ovules 

 in each carpel cavity. The calyx is 

 gamosepalous. 



In the Salvia and the related imints 

 we have the highest development of 

 the Axis Flowers. Compare them with 

 the Buttercups and Magnolias, and 

 note what changes have taken place. 

 The axis has been shortened and reduced; the carpels 

 have been reduced from many and separate to two, 

 united; the stamens, from very many to two; the petals 

 from separate (apopetalous) to united (gamopetalous) ; 

 as well as from regular to irregular; the sepals, from 

 separate to united. 



Laboratory Studies, (a) Examine externally and by cross 

 and longitudinal sections the seeds of Castor Bean (Ricinus), 

 Pea (Pisum), and Squash (Cucurbita), noting the character of 

 the seed coat; the presence of endosperm in Ricinus, its absence 

 in the other two ; and the two cotyledons, and between them the 

 rudiments of the next leaves (the plumule). Where the endo- 

 sperm is lacking note that the cotyledons are thickened into 

 storage organs. 



(6) Germinate some of the foregoing seeds, examining at 

 frequent intervals, and note that in the Castor Bean the thin 

 cotyledons remain in the seeds (in contact with the endosperm) 

 for a longer time than in the Squash, but eventually in both they 

 become green, and function as leaves. In the pea the hemi- 

 spherical cotyledons are too thick to function as leaves, and 

 remain in the seed coats. 



(c) Examine, in sections if necessary, a flower of the common 

 Mallow (Malva), or of Hollyhock (Althaea), or Cotton (Gossy- 

 pium), noting number and arrangement on the torus of the 

 united carpels, united stamens, petals and sepals, bearing in 

 mind the resemblance to and differences from the general plan 

 of the Buttercup type of flower. 



