T. Holm — Ceanothus Americanus and ovatus. 525 



spirally, and the first ones are often merely scale-like and 

 rudimentary ; buds were observed in the axils of the cotyle- 

 dons. In Rh. Frangula, on the other hand, the cotyledons 

 remain enclosed by the seed, and the hypocotyl is very short, 

 but otherwise the development of leaves and buds is the same 

 as in the former species. In Rh. davuricus and Colletia 

 cornuta, described by Lubbock (1. c), the cotyledons are 

 epigeic. 



The seedling of Ceanothus Americanus agrees with that of 

 Rhamnus cathartica so far as concerns the epigeic cotyledons 

 with buds and the presence of a distinct hypocotyl. Our 

 figure 1 shows a seedling where the cotyledons (Cot.) are 

 borne upon an erect hypocotyl (H) ; the epicotyl, the first 

 internode (Ep.), is quite long, and the first two leaves, succeed- 

 ing the cotyledons, show the same outline and venation as the 

 typical leaf of this species, but are opposite (L and L), in con- 

 trast to the others, which are spirally arranged (L 3 — L 4 ). 

 Buds, though very minute, are developed in the axils of all 

 the leaves including the cotyledons. The primary root (R) is 

 long and slender with some of the lateral branches transformed 

 into mycorhizge (M), represented by small globular tubercles. 

 Characteristic of the seedling is thus the presence of cotyle- 

 donary buds, the position of the first leaves (L) being opposite 

 and, finally, the early appearance of the mycorhizge. 



The ramification of the shoot. — During the first season the 

 seedling does not develop any further than the specimen, 

 which we have figured, but the cotyledons fall off in the 

 month of June, and at the end of the season the hypocotyl 

 and sometimes, also, the epicotyl are the only parts remaining 

 above ground, the other internodes having faded away entirely; 

 at the same time the hypocotyl has bent itself downwards to 

 the ground, though without any development of secondary 

 roots. "When the plant is one year old, we notice two oppo- 

 site leaf-bearing shoots (fig. 3) either developed from the axils 

 of the cotyledons or of the opposite leaves, succeeding these, 

 while the main stem (St.) has died off, but remains as a blackish 

 branch. It seems to be the most frequent case that the rami- 

 fication of the shoot takes place by means of the cotyledonary 

 buds, but as stated above, when these do not develop, the buds 

 of the opposite leaves produce the branches. The hypocotyl 

 is now horizontal (H) and the primary root has increased in 

 length and thickness, besides that the mycorhizge are much 

 larger (ML). 



While examining a number of young plants at this stage, 

 we noticed a peculiarity, which seems to be constant in our 

 species. This peculiarity consists in the fact that the greater 



Am. Jour. Sci. — Fourth Series, Vol. XXII, No. 132. — December, 1906. 

 36 



