1 9 1 2] PA CE—PA RNA SSI A 



317 



Saxifraga 



Several species of Saxifraga, growing in the Botanical Garden in 

 Bonn, were examined, to be sure that the usual form of this genus 

 was known. The same methods of fixing and staining were used for 

 Saxifraga, Heuchera, and Drosera as had been employed with 

 Parnassia . 



Juel (14) has given a description of Saxifraga granulata which 

 agrees in all the stages shown with the stages here figured; and I 

 have examined S. ligulata, S. sponhemica, S. cordifolia, and S. 

 crassifolia, which seem to be so similar that the same figures could 

 be used for each. Not much work was done with the reduction 

 division; but the reduced number of chromosomes in S. sponhemica 

 is about 15. Juel (14) found this to be about 30 in S. granulata. 

 These two numbers are rather suggestive, especially since Gates's 

 (10) investigation of Oenothera gigas and Strasburger's (23) 

 discussion of this question. 



Nothing unusual was seen in the pollen development of Saxi- 

 fraga. The pollen grains are small and with smooth, rather thin 

 walls. It might be of interest to note that in many of the flowers of 

 5". cordifolia some of the anthers contained pollen at least twice the 

 usual diameter, and in some cases as much as four times. In one 

 flower this large pollen was found in every other anther, the younger 

 set of stamens all being affected. But not all flowers produced 

 this large pollen, and it was usually irregular in occurrence when 

 present. As all the later flowers were blighted, turning black 

 before the inflorescence was out of the bud, this peculiarity of the 

 pollen was probably due to a fungus; but this was not investigated. 



Two young ovules of S. sponhemica from the same ovary are 

 shown. Fig. 71 shows the archesporial cell, and fig. 72 a later stage 

 in which there is one sporogenous cell and the primary parietal cell 

 has divided. The mother cell stage is shown in fig. 73, with two 

 parietal cells. In fig. 74 there are three sporogenous cells, only one 

 of which has reached the mother cell stage; a later stage is shown in 

 %• 75- There are three parietal cells above the mother cell in fig. 

 76. The whole of this ovule is shown in fig. 79. In Saxifraga, so 

 far as examined, the megaspores are always in a row (fig. 78), and 

 the fourth one develops the embryo sac. Not so much material 



