Typua Insects: THEIR EcoLtoGicaL RELATIONSHIPS 469 
Not every seed in the head of Typha latifolia is perfectly formed or 
fertile. A number of them never become fully mature, and therefore 
could not possibly germinate. It is an easy matter to distinguish the 
fertile seeds in a mature head from the sterile ones. The mature fertile 
seeds lie in a closely fitting pericarp, while the sterile ones are inclosed 
in a pericarp which is developed to more than twice the natural size and 
which has a “hollow” interior with the kernel undeveloped (Plate 
XXXIX, 1). 
In order to determine the approximate percentage of fertility in the 
seeds of Typha latifolia, a number of seeds were picked off at random 
from several heads and by a careful examination the number of fertile 
and sterile seeds was determined. The results of these counts are shown 
in table 3, where it appears that about 75 per cent of the seeds on the 
mature heads are fertile. The heads from which these counts were made 
were picked at random and should represent about average conditions. 
The third head had nearly half of the seeds sterile; the fourth, however, 
nad a high percentage of fertile seeds. 
TABLE 3. DETERMINATION OF THE APPROXIMATE PERCENTAGE OF FERTILITY OF 
TypHa SEEDS 
Number Number | Number Per 
Head of seeds of seeds of seeds cent 
counted fertile sterile fertile 
es 
Loge bo eteb beer 6 Dee rr ares 300 233 6 Uthatl 
2. ccacdeck doe Sone eee 200 156 44 78.0 
oe ec ceh ec dp Cen Oe eS eee et 250 140 110 56.0 
4 oe oe Bue OS DRE eee Et rior core 250 211 39 84.4 
Titel. i: nde re “1,000 GaQie ee 200. 15k oe me 
(SS 
PM CEAPCEDCTECCDL LCTLINC.. 15.5. oe cleicie'e eee [cns > s-sieec|-s2e-s0-- | Re Bere Ayre 74 
Having thus ascertained the approximate percentage of fertility in the 
seeds, experiments were conducted to determine the percentage of 
germination of the fertile seeds. The seeds were placed in covered watch 
glasses, and, though kept in the light, were protected from direct sunlight. 
Germination commenced within a few days after the seeds had been 
placed in the water. Careful counts were made of the number of seeds 
