266 Methods in Plant Histology 



a little above the middle; remove the bud scales, if they promise 

 to cause trouble; retain only enough tissue at the base of the bud 

 to hold the parts in place. Fix in formalin alcohol and stain in 

 safranin and light green. 



Epidermis stripped from the leaf, fixed in 10 per cent formalin 

 in water for a day or two, and then stained in safranin and anilin 

 blue, will give excellent views of stomata. The development of 

 stomata is particularly well shown in Sedum purpurascens, even in 

 leaves which have reached the adult size. The epidermis is very 

 easily stripped from a leaf of Sedum. 



Floral Development. For a study of floral development very 

 young buds are necessary, and it is best to select those forms which 

 have rather dense clusters of flowers, in order that a complete series 

 may be obtained with as little trouble as possible. 



The usual order of appearance of floral parts is (1) calyx, (2) 

 corolla, (3) stamens, and (4) carpels; but if any of these organs is 

 reduced or metamorphosed, their order of appearance may be 

 affected. 



Floral development is easily studied in the common Capsella 

 bursa-pastoris. The best time to collect material is late in March 

 or early in April. Dig up the plant, carefully remove the leaves, 

 and in the center of the rosette a tiny white axis will be found. A 

 series of these axes from 3 to 9mm. in length, and from 1.5 to 

 3.5mm. in diameter will give a very complete series of stages in 

 the development of the floral organs. Preparations from the apex 

 of the shoot taken after the inflorescence appears above ground are 

 not to be compared with those taken early in the season, because 

 the pedicels begin to diverge so early that median longitudinal sec- 

 tions of the flowers are comparatively rare. Fix in chromo-acetic 

 acid and stain in Delafield's haematoxylin. The sections should be 

 longitudinal and about 5 JJL thick. Capsella shows the hypogynous 

 type of development. The order of appearance of floral parts is 

 (1) calyx, (2) stamens, (3) carpels, and (4) petals. The ovary is 

 compound (syncarpous) . 



Ranunculus, which is also hypogynous, will illustrate the develop- 

 ment of the simple (apocarpous) ovary. The ovules appear quite 



