52 UniversH !J of CdJifornia Puhlicatiutis in Bofaini [Vol. 7 



early ai)pe'arane(' of i)ollcii in 7'. ovatain has a i)ai'all('l in tliosc plants 

 of T. grandifiorum, reported hy Atkinson (liSi)9), whose pollen was 

 fully matured in September. It is also interesting to note here two 

 statements which have been made with regai-d to the size of the flower- 

 bud in Eastern species of Trillium the season before flowering. Foerste 

 (1892) states that the largest bud of T. erythrocarpum Michx. which 

 he collected in (.-onnecticut in August was 5.5 mm. long, quite com- 

 parable in relative size to buds of T. sessile var. giganteum in June. 

 Smith (1896) states that a flower-bud of T. grandi/loriiin found in 

 central New York on July 11 was 2 luni. long witli anthers 1.7 nun., 

 such a bud as one can find in T. sessile var. giganteum early in ]May. 



IV. The Dormant Period, Augitst to January 



a. Trillin))! sessile var. giganteum 



The season from August to January inclusive is to be called the 

 dormant season, in the present paper. The terra "dornuint season"' 

 is again used here simply for convenience, just as the term "active 

 season" is used to designate the season from January to J\dy inclusive. 

 Many plants, as previously noted, cease their activity above ground 

 in May or earlier, while, on the other liand, others are appearing above 

 ground in November or earlier. Generally speaking, however, the 

 season from August to January inclusive is the season in which 7'. 

 sessile var. giganteum, growing in the vicinity of San Francisco Bay, 

 has no green leaves above ground. 



This season may be divided into two parts, a season of decreased 

 activity and a season of increased activity. The first division con- 

 tinues until the beginning of the rainy season, late in September or 

 early in October. As noted above, the period May to July is one of 

 active and continued growth, resulting in the differentiating out of 

 the floral organs. During the period August to late September, the 

 dryest season of the year, development is practically at a standstill, 

 while with the opening of the rainy season growth becomes even more 

 rapid than during the period May to July. The period of decreased 

 activity is, however, characterized by the cutting off of the pollen 

 mother-cells and a resting stage preliminary to their rounding up and 

 entering upon the prophases of the meiotic divisions. The last sonmtic 

 divisions in the sporogenous tissues, giving rise to the full number of 

 pollen mother-cells, are completed in the latter part of August and 



