12 University of California Pnhlications in Botany [^o^. 7 



a condition in i-atlicr strikinf? contrast to lliat exhibited hy T. ovatum 

 whieli almost witlioiit cxccpi ion produces an abundance of seed. In 

 California it is diftieult. unless llie plants are staked in the spring 

 wlien in leaf and flowei'. to liml tlieir drying remnants when they 

 are covered witli oilier larger species wliich have dried down over 

 them. Tt has, iiowever, been apparent throughont our field and 

 garden studies that many ]>lants of sessile do not bear fruit either 

 in a given season or during a number of seasons. Indeed, for some 

 years we did not succeed in finding a single fruit containing seeds, 

 though many plants known to have ])roduced apparently normal 

 flowei-s were under observation in the tield as they ripened down. Fur- 

 tliei'. many other- plants examined near tlie close of their active sea>;on 

 above ground were found to mature only a shrunken, undeveloped 

 pistil provided with rudimentary ovules, though these same plants had 

 been strong in appearance and vigorous in growth and at anthesis 

 were provided with pollen and ovules normal in appearance. Again, 

 there are still other plants in the flowers of which at anthesis the 

 pistil is entirely undeveloped. The undeveloped flowers referred to 

 above represent the extreme case of sterility accompanied by the lack 

 of development of all the flower parts. Finally, the almost complete 

 absence of seedlings and young plants, other than those derived 

 vegetatively from older rootstocks, added evidence in support of the 

 contention that lack of seed production was the rule. These earlier 

 observations were confined to stations in the Berkeley hills which by 

 reason of accessibility were favorable for following closely the more 

 obscure periods in the annual life-cycle of the plants. The white- 

 flowered form of var. giganteum characteristic of the northern coast 

 counties has moi-e recently been found to seed rather profusely in 

 certain localities or under certain conditions. More recently, also, 

 a number of i)laiits of sessile in the Berkeley hills have been found 

 to give viable seed, particularly favorable seasons climatically being 

 perhaps responsible. In general, however, it can be said that sessile, 

 in contrast to ovatum, is an extremely uncertain producer of seed 

 and that a very considerable number of individuals are not capable 

 of seed production over a course of a number of years. 



The fact, as noted above, that plants which apparently produced 

 normal sexual elements failed to form fruit led to an experimental 

 and cytological investigation of the causes of sterility in such cases. 

 In the garden a considerable number of flowers were self-pollinated 

 at different periods before and after anthesis. Cross-pollinations, 



