This paper presents the results of cytological observations on microsporogenesis in the self-sterile species Coffea canephora. It was found difficult to study chromosome structure in the first stages of meiosis because the chromosomes do not stain well with aceto carmine and could be seen only as long faintly threads with some heteropycnotic regions. In many observations of the pachytene stage it was possible to observe and study a chromosome attached to the nucleolus. This chromosome characteristically had a visible centromere which divided it into two arms of different sizes. The short arm was attached to the nucleolus and had several heteropycnotic regions. In the long arm the heteropycnotic regions were observed to be close to the centromere ; the distal portion of this arm was only faintly stained. Other chromosomes in the pachytene stage were found to have a conspicuous centromere located between two highly heteropycnotic regions. The heteropycnotic regions in some chromosomes were located near the centromere while in others they were observed to be scattered throughout the chromosome. In diakinesis the chiasmata were counted and there were found seven chromosomes with one chiasma, three chromosomes with two chiasmata and one chromosome with three chiasmata. The average number of chiasmata per cell was 15.88. In metaphase the average number of chiasmata per cell was found to be 14.57, which is less than the average per cell in diakinesis. Anaphase I appeared normal as did all subsequent phases of meiosis, that resulted finally in the development of four microspores with eleven chromosomes each. Very few pollen mother cells with abnormal numbers of chromosomes were observed. On the basis of this study, it is concluded that microsporogenesis in Coffea canephora is normal.

A study has been made of the embryo sac in self-sterile Coffea canephora flowers of different ages. The process was observed to be normal and included the formation of two synergides and one egg cell in the micropilar region, three antipodals at the chalazal region and two polar nuclei lying in the middle of the sac. It is known that in the species C. arabica the embryo sac formation is complete at the time the flowers open. Embryo sac formation in C. canephora is slightly delayed and it is not complete until the day following opening of the flowers. It was also determined that in C. canephora shedding of pollen begins shortly after the flowers open and the pollen was functional at least for two days. Thus the results of the present study indicate that the self-sterility of C. canephora flowers is not due to the delay in formation or abnormal development of the embryo sac.

No gênero Aloë, tôdas as espécies estudadas citològicamente até o presente (cêrca de 90) têm 2n = 14 cromossômios. Em uma forma não classificada, a microsporogênese e a gametogênese foram detalhadamente estudadas. O fato mais interessante constatado é o de se associarem, nos grãos de pólen, os núcleos vegetativo e reprodutivo, sem, contudo, se fundirem. Nos tubos polínicos êles de novo se separam, e o reprodutivo dá formação a dois gâmetas. O número e a morfologia dos cromossômios foram estudados em raízes e em grãos de pólen : o complemento cromossômico é constituído por quatro pares de cromossômios longos, bem identificados, e três pares de cromossômios curtos. Um dos cromossômios longos possui um satélite distal; um dos cromossômios curtos possui um satélite proximal, porém apenas em um dos elementos. Um máximo de três nucléolos nos núcleos somáticos de raízes foi constatado, concordando com a existência de três cromossômios com satélites. O fato de ser esta forma heterozigota, para um dos pares de cromossômios curtos, indica que se deve tratar de um híbrido. O estudo botânico revelou que ela apresenta alguns caraterísticos de A. macracantha e outros de A. saponaria. Da espécie A. macracantha, sabe-se apenas que tem sete pares de cromossômios. A. saponaria, com igual número de cromossômios, é uma das três únicas espécies estudadas que possuem satélites no par de cromossômios curtos. Pode-se, então, deduzir, com relativa segurança, que A. saponaria é uma das espécies que entram na constituição desse híbrido. A outra espécie, muito provàvelmente, será A. macracantha.

In this paper the results are presented of a study of microsporogenesis and gamete formation in an unclassified form of Aloë. This form of Aloë was found to have 2n = 14 chromosomes, a condition which is characterestic of all of the species of this genus that have been examined cytologically. The most interesting observation made in the present study was the constant association, but no fusion, of the vegetative and reprodutive nuclei inside the pollen grain. It was also noted that this association disappears when the nuclei enter the pollen tube. The reproductive nucleus in the pollen tube gives rise to two small male gametes. This paper also includes a description of the morphology of the chromosomes as studied in the root tip cells and in pollen grains. In the form of Aloe studied there are 4 pairs of long chromosomes and 3 pairs of short ones. One pair of the long chromosomes was found to be homozygous for a satellite at the distal arm and one pair of short chromosomes was determined to be heterozygous for a satellite at the proximal arm. It was also observed that there was a maximum of three nucleoli in each somatic cell nucleus which agrees with the existence of three satélites. The cytological observations made indicate that the Aloë plant studied is a hybrid. Also a botanical analysis revealed that this form of Aloë has some characters of A. saponaría (one of the few species with satellites in short chromosomes) and some characters similar to those of A. macracantha. On the basis of the present investigations then, it seem highly probable that the form of Aloë studied is a hybrid between the two above mentioned species.

Após fazer a revisão de alguns dos principais trabalhos sôbre a auto-esterilidade no gênero Coffea efetuados em Java, foram relatados, de modo resumido, os resultados das pesquisas genéticas e citológicas que estão sendo feitas com os exemplares da espécie C. canephora no Instituto Agronômico de Campinas. Êstes estudos têm por finalidade conhecer o grau e as causas da auto-esterilidade dessas plantas. As autopolinizações realizadas indicaram que êsses cafeeiros são, realmente, auto-estéreis. Dos cruzamentos feitos, cerca de 50% se mostraram compatíveis. Tanto a formação do saco embrionário como a do pólen são normais. Em meio artificial conveniente, o pólen apresenta cêrca de 55% de germinação, o que foi considerado suficiente para promover a fertilização nos cruzamentos feitos. Foram realizadas observações sôbre o crescimento do tubo polínico em estilos de flores polinizadas com pólen estranho, compatível, e polinizadas com o próprio pólen. Nos cruzamentos compatíveis, o crescimento do tubo polínico é normal. No segundo oaso notou-se que, após a germinação, o tubo polínico tem o crescimento paralisado, não ultrapassando a região das papilas estigmáticas. Esta pode ser considerada a explicação da auto-esterilidade nos exemplares de C. canephora estudados. O mecanismo genético que controla o crescimento dos tubos polínicos ainda não pôde ser estabelecido. Entretanto, pesquisas estão em prosseguimento no sentido de se verificar se se trata de um mecanismo genético semelhante ao encontrado no gênero Nicotiana.

This paper presents a review of pertinent literature related to studies of self-sterility in the genus Coffea and reports the results of cytological and genetic studies carried out on the species C. canephora at the Instituto Agronômico, Campinas, Brasil. The objetive of the study was to determine the degree and causes of self-sterility in the species C. canephora. In tests involving a large number of self-pollinations in flowers of this species, all were self-sterile and formed, no seed. In tests of cross-pollinations involving C. canephora approximately 50 percent were effective in the formation of seed. Cytological studies showed that the formation of the embryo-sac and pollen grains in C. canephora can be considered normal. Likewise a study of the pollen of this species on artificial media under controlled conditions, showed 55 percent germination and this was considered sufficient to bring about fertilization. In contrast, the cytological investigations of self-pollinated flowers showed that the number of pollen grains that germinated was very small and of those that did germinate, the formed pollen-tube was short and did not extend beyond the stigmatic papillae. Observations on compatible cross-pollinations on C. canephora showed that a large number of pollen grains germinated and that usually there were several pollen-tubes within the style. However, the rate of growth of pollen-tubes in C. canephora was found to be much slower that in C. arabica. The present investigation has shown that in flowers of C. canephora there is a very high degree of self-sterility and this has been related to poor germination of the pollen grains and subsequent limitation in the development of pollen tubes.