1918] Alterxation axd Paktiiexogenesis ix Padixa 87 



Since 7 cultures of tetraspores were successful, whereas only 3 from 

 unfertilized eggs gave mature plants, the conditions being identical, 

 it must be assumed that the failure to produce mature plants on the 

 part of at least 4 cultures of unfertilized eggs can only be explained 

 by assuming that they were incapable of doing so. The few plants 

 which were produced are probably due to chance spores falling into 

 depressions on the shells, even though they were placed on edge, 

 except perhaps some of the tetrasporic individuals — these latter to 

 be referred to later. 



In 1914 and 1915 control experiments were carried through in 

 order to see the relation between the plants produced by spores which 

 simply chanced to fall from Padina in the vicinity of the cultures. 

 These controls were simply cleaned oyster shells, without reproduc- 

 tive elements of any kind upon them, attached alongside and there- 

 fore exposed to the same conditions as those bearing sporelings. The 

 results are given in Tables 7 and 10. It will be noticed that male 

 1)1 ants are most numerous, females less so, and tetrasporic least of 

 all. It might be assumed that they should be equally numerous, as 

 they are apparently so in nature. An examination of the various 

 cultures will show that females are larger before beginning to fruit 

 than males, and that tetrasporic plants are usually still larger, gen- 

 erally, than either males or females. Table 11, for exami)le, shows 

 but 2 females fruiting below 20 millimeters in length, whereas G 

 males of this siz(> are thus found. This relation, however, is not 

 evident in all eases, and in particular cultures it is even sometimes 

 reversed, but a careful calculation based on a large number of indi- 

 viduals bears it out. In Table 8, for instance, there are only «'.«; 

 females fruiting below, to 3K5 above, 20 inni. in size. If the ratio 

 for males, 89 to 337, should have been maintained, wc should have 

 had 83 instead of 6G. In all the tables relatively few fruiting tetra- 

 sporic plants are found below 20 mm. in length. This ditTerence in 

 size at which the dilVenMit ])hints |)ro(lnc(' r('pi-o(luftivc hoijics is be- 

 lieved to account f(n- the slight ])r('ponderancc in numbers of males 

 over females, and both over tetrasporic individuals. In other words, 

 there are anion"- the voung sterile individuals enough fennile and 



