EVANS—THE NORTH AMERICAN SPECIES OF ASTERELLA. 257 
longitudinally split at a comparatively early age, the splits beginning 
close to the apical pore and extending for a variable distance toward 
the base. In most cases the segments thus formed remain united at 
the apex, the wind sifting in between them and thus scattering the 
spores; but in a few species the segments become completely free 
with age. The number of segments varies usually from 8 to 16 but, 
more rarely, between wider limits. .A good deal of variation, in fact, 
is sometimes encountered in a single species. With regard to color, 
also, the pseudoperianth varies. In certain species it is, apparently, 
always colorless; in others, such as A. lindenbergiana, it shows a deep 
purple pigmentation; in still others it may be colorless, or pigmented 
in varying degree. Although so distinctive for the genus as a whole, 
the characters derived from the pseudoperianth often have to be em- 
ployed with considerable caution in distinguishing species. . 
If Goebel’s ideas are to be accepted, the distinct discoid androecium 
found in certain autoicous species represents the most primitive type, 
because it approaches most closely the stalked androecia of Mar- 
chantia and Preissia. The median elongated androecia, with or with- 
out paleae, would then represent a more advanced type which has 
arisen through reduction, and the poorly defined androecia of the 
paroicous species would represent the most advanced condition found 
in the genus. A gradual loss of the power of limiting growth would 
be associated with this reduction. Of course here, as in other genera, 
the female receptacle is more conservative than the male, retaining 
its stalk even when the androecium has almost lost its individuality. 
It retains also its compound pores, which have come down to it from 
its more complex ancestors, while the androecia seem to have lost 
them altogether. 
Similar deductions might be drawn from the related genus 
Grimaldia, although the conditions shown are less diverse. In G. 
fragrans (Balb.) Corda, for example, the androecium is much the 
same as in A. elegans, while in G. dichotoma Raddi it bears a strong 
resemblance to that of A. pringlei. Here again the epidermal pores 
are of the simple type. So far as the androecia are concerned, fe- 
boulia occupies a somewhat intermediate position between the more 
complex genera and Asterella. The androecia are clearly defined, as 
in A. elegans, and often limit the growth of the branches bearing 
them, but they still show epidermal pores of the compound type; 
these pores, however, are composed of fewer tiers of cells than those 
of the female receptacle." 
The sporophyte is of the type characteristic of the Operculatae. 
It consists of a bulbous foot, an exceedingly short stalk, and a rela- 
See Cavers, Naturalist 1904: 248. f. 4. 1904. 
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